Interview questions and answer, Network security

Questions for Network Engineer / Network Administrator (Security)

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February 7, 2017

Top Interview Questions for Network
Engineer / Network Administrator (Security)

Are you looking for job as a Network Security Engineer? Or are
you thinking of leaving your current position and considering a new job as
Network Engineer/Administrator with a new company in LAN/WAN Network Security environment?

If yes, then this article is for you and any of described
technologies and questions may be asked during the interview!

Network Engineer/Administrator (security) is a higher-level position,
often with “jr.” and “sr.” prefixes. The major responsibility of a network
engineer (security) is to determine “how to implement network security” in
routed LAN/WAN environments. They design and implement both the hardware and
software necessary technologies to secure computer network. They have
high-level technical skills in LAN/WAN security. The major responsibility of a
network admin (security) includes adding security software and hardware,
performance monitoring, troubleshooting, logging errors, backing up and restoring
data, and assigning permissions to users.

Before facing any interview for a network engineer/administrator
(security) position, make sure that you have enough knowledge of firewalls
(software & hardware), VPNs (IPsec, SSL, and Get VPN etc.) with general
network technologies as described below:

Network concepts:

·
* Data communication and transmission techniques

·
* Fundamentals of OSI & TCP/IP model

·
* Router’s basic operations (startup, nvram, flash/IOS backup
& recovery)

·
* IP Addressing and Summarization

·
* IP Routing : Basics of RIP , EIGRP , OSPF & BGP

Firewall

·
* NAT (object based)

·
* ACL (object based)

·
* Contexts

·
* Failover (Active-Standby & Active-Active)

·
* Transparent

·
* MPF (Modular Policy Framework)

VPN

·
* Site to Site

·
* SSL

·
* Get VPN

·
* Easy VPN

·
* DMVPN

·
Flex

Route-Filtering

·
* Access-lists

·
* Route-Maps

·
* Prefix-Lists

·
* Distribute-Lists

·
* Filter-lists

·
* Class-maps & Policy-maps

Network security

·
* AAA Server

·
* Dot 1x Authentication

·
* Ip SLA

Questions for an Interview of
Network Security Engineer/Administrator:

All listed questions are very common and important and you must
be prepared with all of the following answers before facing any interview for a
Network Security position.

Q. What is a firewall?

A: A firewall is used to provide security to the private
networks connected to the internet. They can be implemented as hardware or
software, or a combination of both. All incoming and outgoing network traffic
are examined and accepted/rejected by the firewall as per defined rules.

Q. What is the difference between network gateway and a firewall?

A: A network gateway joins two networks together and a network
firewall protects a computer network against unauthorized incoming or outgoing
access. Network firewalls may be hardware devices or software programs.

Q. What is the difference between IPS and a firewall?

A: The primary function of a firewall is to prevent/control
traffic flow from an untrusted network (outside). A firewall is not able to
detect an attack in which the data is deviating from its regular pattern,
whereas an IPS can detect and reset that connection as it has inbuilt anomaly
detection.

Q. What is a transparent firewall?

A: A transparent firewall is considered as Layer 2. Deploying
a new firewall into a network can be a complicated process due to various
issues (e.g. IP address reconfiguration, network topology changes, current
firewall etc.) because the firewall is not a routed hop and you can easily
introduce a transparent firewall into an existing network.

Q. What is packet filtering?

A: Packet filtering is the process of permitting or blocking
ip packets based on source and destination addresses, ports, or protocols. The
packet filter examines the header of each packet based on a specific set of
rules, and on that basis, decides to prevent it from passing or allow. Packet
filtering is also part of a firewall program for protecting a local network
from unwanted access.

Q. Define stateful inspection?

A: Stateful inspection is known as dynamic packet filtering
and is a firewall technology that monitors the state of active connections and
uses this information to determine which network packets are allowed through
the firewall. Stateful inspection analyses packets down to the application
layer.

Q. What is the Public Key Encryption?

A: Public key encryption uses public and private key for
encryption and decryption. In this mechanism, public key is used to encrypt
messages and only the corresponding private key can be used to decrypt them. To
encrypt a message, a sender has to know the recipient’s public key.

Q. Define Digital Signatures

A: Digital signature is an attachment to an electronic
message used for security purposes. It is used to verify the authenticity of
the sender.

Q. What is Authorization?

A: Authorization is a security mechanism used to determine
user/client privileges or access levels related to network resources, including
firewalls, routers, switches and application features. Authorization is
normally preceded by authentication and during authorization. It’s system that
verifies an authenticated user’s access rules and either grants or refuses
resource access.

Q. What is stateful failover?

A: Every time a session is created for a flow of traffic on
the primary node, it is synced to the secondary node. When the primary node
fails, sessions continue to pass traffic through the secondary node without
having to re-establish.

Q. What is VPN and describe IPsec VPN

A: Virtual Private Network (VPN) creates a secure network
connection over a public network such as the internet.

IPsec VPN means VPN over IP Security allows two or more users to
communicate in a secure manner by authenticating and encrypting each IP packet
of a communication session.

Q. What is Site to Site and remote access VPN?

A: A site-to-site VPN allows offices in multiple locations to
establish secure connections with each other over a public network such as the
Internet. Site-to-site VPN is different from remote-access VPN as it eliminates
the need for each computer to run VPN client software as if it were on a
remote-access VPN.

Q. How do you check the status of the tunnel’s phase 1 & 2 ?

A: Use following commands to check the status of tunnel
phases:

Phase 1 : show crypto isakmp and State : MM_ACTIVE

Phase 2 : show crypto ipsec sa

Note: if you have lot of tunnels and the output is confusing use
a ‘show crypto ipsec sa peer 12.12.12.12′ command instead.

Q. What is SSL VPN? How it is different from IPsec VPN?

A: SSL VPN provides remote access connectivity from almost
any internet enabled location without any special client software at a remote
site. You only need a standard web browser and its native SSL encryption.

IPsec is a dedicated point-to-point fixed VPN connection where
SSL VPNs provides anywhere connectivity without any configuration or special software
at remote site.

Q. What is GRE and why is it required?

A: Generic Routing Encapsulation (GRE) is a protocol that
encapsulates packets in order to route other protocols over IP networks.

GRE enables a wrapper to be placed around a packet during transmission
of the data. A receiving GRE removes the wrapper, enabling the original packet
to be processed by the receiving stack.

Advantages of GRE tunnels include the following:

·
* GRE tunnels connect discontinuous sub-networks.

·
* GRE tunnels allow VPNs across wide area networks (WANs).

·
* GRE tunnels encase multiple protocols over a single-protocol
backbone.

·
* GRE tunnels provide workarounds for networks with limited
hops.

Q. Firewalls work at what layer? Define firewall generations and
their roles.

A: Firewalls work at layer 3, 4 & 7. First generation
firewalls provide packet filtering and they generally operate at layer 3
(Network Layer). Second generation firewalls operate up to the Transport layer
(layer 4) and records all connections passing through it and determines whether
a packet is the start of a new connection, a part of an existing connection, or
not part of any connection. Second generation firewall is mainly used for
Stateful Inspection.

Third generation firewalls operate at layer 7. The key benefit
of application layer filtering is that it can “understand” certain applications
and protocols (such as File Transfer Protocol (FTP), Domain Name System (DNS),
or Hypertext Transfer Protocol (HTTP)).

Q. What is DoS attack? How can it be prevented?

A: DoS (Denial of Service) attack can be generated by sending
a flood of data or requests to a target system resulting in a consume/crash of
the target system’s resources. The attacker often uses ip spoofing to conceal
his identity when launching a DoS attack.

Q. What is IP Spoofing?

A: An IP spoofing attack enables an attacker to replace its
identity as trusted for attacking host. For example, if an attacker convinces a
host that he is a trusted client, he might gain privileged access to a host.

Q. What are the security-levels in cisco ASA?

A: ASA uses security levels to determine the parameters of
trust given to a network attached to the respective interface. The security
level can be configured between 0 to 100 where higher number are more trusted
than lower. By default, the ASA allows packets from a higher (trusted) security
interface to a lower (untrusted) security interface without the need for an ACL
explicitly allowing the packets.

Q. What is AAA?

A: AAA stands for authentication, authorization and accounting,
used to control user’s rights to access network resources and to keep track of
the activity of users over a network. The current standard by which devices or
applications communicate with an AAA server is the Remote Authentication
Dial-In User Service (RADIUS).

Q. What is IPS? How does it work?

A: An Intrusion Prevention System (IPS) is a network
security/threat prevention technology that examines network traffic flows to
detect and prevent vulnerability exploits. An Intrusion Prevention System can play
a good role to protect against various network security attacks such as brute
force attacks, Denial of Service (DoS) attacks, and vulnerability detection.
Moreover, an IPS also ensures prevention against protocol exploits.

Intrusion Prevention System uses four types of approaches to
secure the network from intrusions which include:

·
* Signature-Based

·
* Anomaly-Based

·
* Policy-Based

·
* Protocol-Analysis-Based

The above described questions are very tricky and important in
aspect to clear any interview for Network Security Engineer/Administrator
position and it is not possible for anyone to explain all kind of questions so
you can download more questions from the download link posted here and if you
find any difficulty getting the answer to any question then you can write me @
Comment section.

Top Interview Questions that Network
Design Engineer Candidates Need to Know

Are you looking for job as a network design engineer? Or are you
thinking to leave your current position for a new job as a network designer with
a new company?

If you answered yes to either of those questions, then this
article is for you and any of the described technologies and questions may be
asked during the interview!

Network design engineer is a higher-level position; the major
responsibility of a network design engineer is to design both the hardware and
software technologies needed for a company’s network setup. A network designer
examines vendor-agnostic network design principles and is often responsible for
designing all of the network infrastructure, including routing, switching,
security, LAN, WAN, VoIP, wireless, optimization, load balancing, etc. If you
are more interested in network design and architecture, then don’t walk away
from the equipment, open up your brain to new approaches building networks.

The scope of network designing is enormous (going through almost
all networking specialization).

A network design engineer must have the knowledge of the
following technologies:

·
* Layer 2 control plane

·
* Layer 3 control plane

·
* VoIP, security, wireless network architecture

·
* Network virtualization

·
* Design considerations

·
* Analyze design requirements

·
* Develop and Implement network designs

·
* Validate and optimize network design

I have read somewhere “there are those who design networks….
very large networks who may not do one ounce of actual installation or
implementation of the network.”

Yes, it is possible that a person who has never worked on
network technologies or seen even a router or switch can be a network designer.
Equally, there are people who lay cables and configure routers and switches all
day. In the middle ground are the amateur designers who will throw a solution
together based on nothing but experience and reality, so it depends where you
want to be as a network engineer.

The network designer in general focuses on the “Why“, where the network engineer
(implementation) focuses on “How.” Designing track gives you concepts and processes that will
enable you to better plan and lay out a network. It also gives you concepts such
as the design lifecycle, network lifecycle, etc. It attempts to teach you
different methodologies to sort through design problems and how to tackle them.

Also, the network designer has very broad technical knowledge
where he/she needs strong logical and technological points of view because
he/she needs to design with wireless, voice, and security in mind and not just
routing and switching.

My Best Questions for an Interview of Network Design Engineer

All of the questions below are very common and must be prepared
for before facing any interview for the network designing environment.

Q: What is your experience as a network design engineer?

A: You can answer with your wealth of network experience and job
responsibilities and don’t forget to share your achievements as a network
design engineer. You can also mention your involvement in complex LAN, WLAN,
and IPT infrastructure solutions and large-scale projects in unique
environments with collaboratively working within a team.

Basically, a network design engineer works with project teams,
takes information and/or project specifications from customers and turns it
into a completed design definition which meets the agreed specification, with
due consideration to factors such as security and operational support including
routing, switching, security, LAN, WAN, VoIP, wireless, optimization, load
balancing, etc.

Q: What decisions/suggestions you have made as network design
engineer?

A: Here you can provide the information on major
suggestions/decisions taken by you on network/device migration and up-grading
from your previous experience. You can also share your involvement in project
review meetings and regular representation of the network services with your
team, and how it helped your team to achieve organizational goals of network
services.

Answer the question with all of positive decisions/suggestion
taken by you and don’t try to explore decisions that were wrong in term of
technical or any misfit technology but this doesn’t mean that you will not
share your creativity and solution development skills.

Q: Describe the set of required skills for a network design
engineer?

A: Answer this question with the description of required key skills
for a network engineer as listed below;

• Layer 2 control plane
• Layer 3 control plane
• VoIP, security, wireless network architecture
• Network virtualization
• Design considerations
• Analyze design requirements
• Develop and implement network designs
• Validate and optimize network design

Q: Describe techniques you used as a network design engineer?

A: This question is asked very often during the interview for
network designing position.

You must prepare the answer before facing the interview. You can
start your answer with a list of technologies used by you. You might have to
face cross-questioning for the described list of technologies.

You will be expected to share challenging timescales and
demonstrate flexibility and sound design principles that allow your employer to
meet the requirements of network project. You can also share your best-practice
design methods that helped you to update and improve your way of working.

Q. How do traceroute and ping work?

A: Traceroute is a network debugging utility that attempts to trace the
path a packet takes through the network. when you execute a traceroute command,
your machine sends out 3 UDP packets with a TTL (time-to-live) of 1.

Traceroute works by increasing the “time-to-live” value of each
successive batch of packets sent. This keeps going until you reach the
destination.

Ping: It sends an ICMP (Internet control message protocol) echo
request to a specified interface on the network and, in response, it expects to
receive an ICMP echo reply. By doing this, the program can test connectivity,
gauge response time, etc.

Q: How many channels are in E1 and T1 link and what is the
operational bandwidth of each channel in each link?

A: E1 link contains 32 channels while T1 link contains 24
digital channels and each channel of both T1/E1 gives you 64 kbps bandwidth.

An E1 link consists of 30B channels and 1D channel and each
channel has 64k Bw.

So for E1 – you get 30*64 = 1920kbps

A T1 link consists of 23B channels and a D channel and each
channel has 64k Bw. So for T1 – you get 23*64 = 1472kbps

Q. What are the main contents of a routing table?

A: A routing table contains the information necessary to
forward a packet along the best path toward its destination.

A basic routing table includes the following information:

·
* Destination network-id

·
* Next hop

·
* Exit Interface (outgoing network interface)

·
* Administrative distance:

·
* Metric: Assigns a cost to each available route so that the
most cost-effective path can be chosen

Q: What is a route flap?

A: Route flapping occurs very often in computer networking
when a router alternately advertises a destination network via one route then
another in quick sequence; also if an interface on a router has a hardware
failure, it will cause the router to announce it alternately as “up” and
“down”.

Q: What basic set-up equipment is needed for VoIP?

A: For general VoIP set up we require the following things;

·
* Broadband connection

·
* VoIP phone*

·
* Nexton soft-switches

·
* Router

·
* Audiocodec

·
* Astric server

Q: Why do we use BGP?

A: Border gateway protocol is an exterior gateway protocol
(EGP) used for routing between autonomous systems. TCP port 179 is used to
establish session

We can use BGP in the following conditions:

·
* Customer is connected to multiple Internet service providers
(ISPs).

·
* Service provider networks (Transit autonomous system).

·
* In very large enterprise networks, where we can use BGP at
core layer as a redundant routing protocol.

Q: Describe what a VPN is and how it works.

A: Virtual Private Network (VPN) creates a secure network
connection over a public network such as the Internet. IPsec VPN means VPN over
IP Security allows two or more users to communicate in a secure manner by
authenticating and encrypting each IP packet of a communication session.

Q: What are delay, jitter and packet loss and how can we overcome
these issues?

A: Network traffic often suffers from one or more of the following
issues:

Delay: Excessive time required for a packet to traverse the network

Jitter: The uneven arrival of packets, considered as delay variation

Packet loss: Dropped packets are not retransmitted

QoS can be used to overcome these issues, especially for unified
communication network traffic. A commonly used IntServ QoS tool is RSVP
(resource reservation protocol), which provides QoS by guaranteeing treatment
to a particular traffic flow.

And DiffServ QoS tool classifies different types of traffic and
provides different levels

of service based on those distinctions.

Q: Describe high-level and low-level network design.

A: A HLD is referred to as software architecture; it provides
an overview of solution, platform, system, product, or process. High-level
design involves decomposing system into modules and representing the interfaces
and invocation relationships among modules. A high-level design document will
usually include a high-level architecture diagram depicting the components,
interfaces, and networks that need to be further specified or developed.

LLD, also known as detailed design, is used to design internals
of the individual modules identified during HLD. LLD describes each and every
module in an elaborate manner so that the engineer can directly implement the
network based on this.

Top Interview Questions for Network
Engineer-Administrators (Data-WAN)

Are you looking for job as a network engineer/network
administrator? Or are you thinking to leave your current position for a new job
as a network engineer/administrator with a new company in a routed LAN/WAN
environment?

If you answered yes to either of those questions, then this
article is for you and any of described technologies and questions may be asked
of you during the interview!

Network Engineer is a higher-level position, often with a “junior” or
“senior” prefix. The major responsibility of a network engineer is to determine
“how to implement technologies” in a routed LAN/WAN environment. They design
and implement both the hardware and software technologies needed for a computer
network. They have high-level technical skills in local area networks (LANs) or
wide area networks (WANs).

Network Administrator is responsible for the smooth, efficient, and secure
operation of computer networks. In general, they configure and administer
existing networks rather than designing networks from the beginning. They play
a very challenging role in a routed LAN/WAN environment, including
customization of the network as per the organization’s needs, such as adding
software and hardware, performance monitoring, troubleshooting, logging errors,
backing up and restoring data, assigning permissions to users, and helping
users with network issues.

Before facing any Interview for network engineer/administrator
position, make sure that you have enough knowledge on below technologies.

General network concepts:

·
* Data communication and transmission techniques

·
* Fundamentals of OSI and TCP/IP model

·
* Router’s basic operations (startup, NVRAM, flash/IOS backup
and recovery)

IP addressing and summarization:

·
* IP address classes

·
* Classful and classless IP addresses

·
* IP subnetting

·
* Understating wild card masks

·
* CIDR,FLSM,VLSM

·
* IPv6 fundamentals

Routing:

RIP

·
* Difference between RIPv1,RIPv2 and RIPng

·
* Passive Interface

·
* RIP Timers

·
* RIP AD and Multicast Address

·
* Split Horizon and Route Poisoning

EIGRP

·
* Auto and Manual Summarization

·
* Neighborship Conditions

·
* Passive Interface

·
* Split Horizon

·
* Authentication

·
* EIGRP Stub Routing and Stuck in Active

·
* Equal and Unequal Load Balancing

·
* EIGRP ADs and Multicast Address

OSPF

·
* OSPF Area Types

·
* OSPF Neighborship Conditions

·
* Concepts of ABR and ASBR Router

·
* DR/BDR Fundamentals and Election

·
* OSPF Times and Authentications

·
* OSPF Summarizations (Inter-Area, External, and Default Info
Originate)

·
* OSPF AD and Multicast Addresses

·
* OSPF Network and LSA Types

BGP

·
* BGP Fundamentals – Why and When to Use BGP?

·
* BGP States and Message Types

·
* BGP Neighborship Conditions

·
* iBGP and eBGP

·
* BGP Summarization

·
* Use of Update Source, eBGP-Multi-Hop, Next-Hop-Self Commands

·
* BGP Path Attributes

·
* BGP Synchronization and Split-Horizon Rule

·
* BGP Address Families

·
* BGP Communities

MPLS

·
* MPLS Fundamentals – IP CEF, LIB, LFIB

·
* LDP and TDP

·
* P, PE and CE Routers

·
* PUSH,POP,SWAP Functions

·
* PHP – Penultimate Hop Popping

·
* BGP – VPN

·
* MPLS over ATM /Frame Relay

QoS

·
* QoS Models and Tools

·
* Difference between L2 and L3 Queues

·
* Characteristics of CoS, ToS, IPP, DSCP AF and EF

·
* Class Maps and Policy Maps

Route Filtering

·
* Access-List Fundamentals

·
* Route-Maps

·
* Prefix-Lists

·
* Distribute-Lists

·
* Filter-Lists

IP Services and Network Securities

·
* First-Hop Redundancy Protocols (HSRP,VRRP,GLBP)

·
* Network Address Translation (Static, Dynamic, PAT)

·
* Network Time Protocols, Syslog Server, SNMP

·
* Basics of VPNs (IPsec, Site to Site , DMVPN, Remote VPN)

·
* IP Multicast Routing (IGMP,PIM SM/DM, MSDP)

·
* Policy-Based Routing

·
* IP SLA

My Best Questions for an Interview of Network Engineer/Network
Administrator: All of the questions below are very common and must be
prepared for before facing any interview for the data-WAN environment.

1. What is a router? Or define the basic requirements of a router?

Answer: A router is a layer 3 network device used to establish
communication between different networks. Basic roles performed by a router
are:

·
* Inter-network communication

·
* Best path selection

·
* Packet forwarding

·
* Packet filtering

2. What is the use of routing? or Why we use routing?

Answer: By default, a router provides inter-network communication
only for directly connected networks. To establish communication between
indirectly connected networks, we require ROUTING. We can use static or dynamic
(IGP or EGP) routing, according to topology requirement.

3. Define the criteria for best path selection of a router?

Answer: A router’s routing table contains only best route. To
select a route as best, a router considers the following parameters;

·
* Longest prefix match

·
* Minimum AD (administrative distance)

·
* Lowest metric value

If all listed parameters are the same, then it would
perform equal cost load balancing.

4. Define “stuck in active.”

Answer: If a successor route (best route) fails, then the router
sends a query message to its neighbor demanding a feasible successor (back-up
route) and a query received by the router may be forwarded to other neighbors
that could lead to a loop, as well. The wait for the response of query message
is called “stuck in active” (SIA).

5. Can we use OSPF without backbone area?

Answer: Yes, but it will be limited to intra-area (same area)
communication. By default, Inter-area communication is not possible without
backbone area.

6. What do you mean by OSPF transit area ?

Answer: A transit area is the area that has a virtual link
connecting two or more ABRs attached to this area.

7. What is the difference between an OPPF neighbor and an adjacent
neighbor?

Answer: Neighbors are the routers that are in the same area and
exchange hello packets, but not LSA information. Adjacent routers are routers
that have fully exchanged their LSA information and are stable.

If OSPF state is in 2WAY/DROTHER, it means a neighbor
relationship and, if the state is FULL/DR or FULL/BDR, it means that the
adjacency is formed.

8. BGP neighborship is not coming up. Please define the various
steps to troubleshoot it.

Answer: To troubleshoot BGP, first we need to check neighbor state
using “show ip bgp summary.” If the state is Idle, it means that the peer
address or AS is not defined properly; if the state is Active, it means that TCP port 179
is not open, the peer is not reachable, network congestion, or BGP
misconfiguration.

Common neighbor stability problems of BGP

·
* Misconfigured neighbor’s IP address and AS number

·
* Reachability issues when interfaces other than directly
connected interfaces are used while peering (update-source issue).

·
* Authentication must be properly implemented (if configured)

·
* Router-ID must be unique

You can get more information from my BGP Tshoot article.

9. What is route reflector and why it is required?

Answer: Route reflector is a solution for BGP split horizon. The
rule says “prefix learned from an iBGP neighbor will not be advertised to
another iBGP neighbor.”
To overcome this situation, we have multiple options:

1. Make your network a full mesh

2. Route confederation

3. Confederation

Route reflector is something like a central point acting as a
route reflector server: Rather than peering with every iBGP router in a full
mesh, it makes IBGP neighbors as route reflector clients to overcome the split
horizon issue.

10. What is the difference between standard and extended ACL?

Answer: Standard ACLs are source-based, whereas extended ACLs are
source- and destination-based. Standard ACLs can only filter layer 3 network
traffic, while extended ACLs can be used to filter layer 3 and layer 4, as
well.

11. What is the use of distribute-list?

Answer: To filter a routing database, we use distribute-list,
which can be applied over most routing protocols. This means that, If you don’t
want any specific network in your routing table, then you can use
distribute-list.

12. MPLS works on which layer?

Answer: MPLS operates between layer 2 and layer 3, so it is
sometimes called layer 2.5.

13. What is penultimate hop popping (PHP) and what is its use?

Answer: PHP is the technique for removing the (POP) MPLS label
before the egress router. The MPLS label on a switched packet is popped by
either the egress router or the penultimate router, depending on your
configuration. If you decide to use penultimate hop popping, you essentially
terminate the LSP one hop earlier. The MPLS labels are popped by the routers
that connect to the egress router, rather than all of them being popped by the
same egress router.

14. What is the difference between layer 2 and layer 3 QoS?

Answer: L2-QoS is at the MAC layer and can be applied by using CoS
(class of service) filed in the VLAN header. This will be used to prioritize
traffic. Later, a QOS scheduler can use the COS filed to qualify the traffic
into different QOS queues.

L3 QOS is required for IP level classification; it can be
achieved through ToS (type of service) priority values—IPP (3-bit), DSCP (6-bit),
which can be set in the TOS field of the IP header. This TOS will later be used
by scheduling process to achieve QOS.

L2 queues are hardware-based, while L3 queues are
software-based. That’s why we can modify L3 queues to meet our requirements.

General Network Concepts:

·
* Data communication and transmission techniques

·
* Fundamentals of OSI and TCP/IP model

·
* Basic operations of a switch (startup, NVRAM, flash/IOS backup
& recovery)

IP Addressing & Summarization:

·
* IP address classes

·
* Classful and classless IP addresses

·
* IP subnetting

·
* Understating wild card masks

·
* CIDR, FLSM, and VLSM

·
* IPv6 fundamentals

Basics of Routing

·
* RIP

·
* EIGRP

·
* OSPF

LAN Switching:

VLAN

·
* Basic requirements of VLANs

·
* VLAN Database

·
* Normal/Extended VLAN, voice VLAN

·
* Inter-VLAN routing

·
* Switch Virtual Interface (SVI)

Implement and Troubleshoot Trunking

·
* Trunk encapsulations

·
* DTP (Dynamic Trunking Protocol)

·
* Native VLAN

·
* Manual VLAN pruning

VLAN Trunking Protocol

·
* Requirement and functionalities of VTP

·
* VTP modes/versions

·
* VTP revision number

·
* VTP pruning

·
* VTP authentication

Spanning Tree Protocol

·
* Needs of STP

·
* Switch priority, port priority, path cost, STP timers

·
* PVST and PVST+

·
* RSTP and RPVST

·
* Multi-Spanning Tree (MST)

·
* Spanning Tree Enhancements (PortFast, UplinkFast,
BackboneFast, etc.)

Implement and Troubleshoot Ether-channel

·
* LACP, PAgP, manual

·
* Layer 2, layer 3

·
* Ether-channel Load-balancing

·
* Ether-channel misconfiguration guard

First Hop Redundancy

·
* Hot Standby Routing Protocol (HSRP)

·
* Virtual Routing Redundancy Protocol (VRRP)

·
* Gateway Load Balancing Protocol (GLBP)

L2- QoS

·
* QoS Models and Tools

·
* Layer 2 queues

Layer 2 Network Security

·
* DHCP Snooping

·
* Dynamic ARP Inspection (DAI)

·
* BPDU Guard, BPDU Filter, Root Guard, Loop Guard, UDLD

·
* AAA server

·
* VLAN Access-Maps

·
* Private VLANs

·
* Storm Control

·
* Port-Security

·
* IP Source Guard

Network Services

·
* System Management (VTY, Telnet, HTTP, SSH, FTP, TFTP)

·
* SNMP, Syslog

·
* DHCP client, IOS DHCP server, DHCP relay

Top Interview Questions for a Network Engineer/Network
Administrator (Data – LAN) Position

All of the questions below are very common and must be prepared
for before facing any interview for the data-LAN environment.

Q: What is Ethernet? Define the different types of Ethernet.

A: Ethernet is a physical and data link layer LAN technology for
connecting a number of computer systems with network protocols.
The Ethernet system called 10BASE-T provides transmission speeds of up to 10
Mbps. Devices are connected to the cable and compete for access using a Carrier
Sense Multiple Access with Collision Detection (CSMA/CD) protocol.

Fast Ethernet or 100BASE-T provides transmission speeds of up to
100 megabits per second and is typically used for LAN backbone systems. Gigabit
Ethernet provides an even higher level of backbone support at 1,000 megabits
per second (1 gigabits per second).

Q: What do broadcast and collision domains mean?

A: A broadcast domain is a logical boundary of a computer
network, in which all nodes can reach each other by broadcast in a LAN
environment.

A collision domain is a section of a network where data packets
can collide with one another when being sent on a shared medium.
Only one device in the collision domain may transmit at one time, and the other
devices in the domain listen to the network in order to avoid data collisions.

Q: What are the basic differences between a hub and a switch?

A: Both hubs and switches are centralised devices that connect
multiple network devices over LAN but their functionalities are different. Hubs
operate at layer 1 whereas switches operate at layer 2. Hubs support half
duplex transmission while switches support full duplex. There is one broadcast
and collision domain in a hub, but a switch has one broadcast plus as many collision
domains as the number of switch ports.

A hub operates at Ethernet but switches operate at
Fast-Ethernet/Gig-Ethernet.

Q: What is a switch? What is the difference between manageable and
unmanageable switches?

A: A switch is a multi-port network bridge used to connect
multiple network devices over the same geographical location. It processes and
forwards data at the data link layer (layer 2) of the OSI model.

Unmanaged switches have no configuration interface or options.
They are typically used in small offices or home environments.

A managed network switch is configurable and provides the
control to manage Spanning Tree Protocol, Port Speed, VLANS, etc. They provide
a serial console and command-line access via telnet and SSH, as well as
management via SNMP.

Q: What is VLAN and why is it used?

A: A VLAN (Virtual LAN) is a logical broadcast domain which
allows a network administrator to create groups of logically networked devices
based on functions, departments, or projects. The basic reason for splitting a
network into VLANs is to reduce congestion on a large LAN.

The primary benefits of using VLANs are:

·
* Security

·
* Cost reduction

·
* High performance

·
* Broadcast storm mitigation

·
* Improved IT staff efficiency

·
* Simple project or application management

Q: What is a native VLAN?

A: A native VLAN is an untagged VLAN on an 802.1q trunked switch
port. If a switch receives untagged frames on a trunk port, they are assumed to
be part of the VLAN that are designated on the same switch port as the native
VLAN. Frames that pass through a switch port on the native VLAN are not tagged.

Q: What is VLAN pruning?

A: By default, a trunk port allows all VLANs through the trunk;
all switches in the network receive all broadcasts, even in situations in which
few users are connected to that VLAN. Pruning is a method to prevent flooding
across the network from unnecessary traffic.

Q: Define the role of access and trunk ports.

A: A Switch port plays two common roles as access and trunk.

Access Port: Carries single VLAN traffic. Mostly used to connect end devices
(routers, IP phones, printers, desktops, etc.)

Trunk Port: Transports multi-VLAN traffic. Mostly used between switches
configured with multiple VLANs.

Q: Why do we use VTP and what is the transparent mode in VTP?

A: VTP is a Cisco proprietary switching technology, used for VLAN
database replication in a switching environment. VTP has four modes: server,
client, transparent and off. VLANs created on a VTP server synchronises with
VTP clients automatically.
The VTP configuration has a revision number which will increase when you make a
change on a VLAN database.

VTP Transparent switches forwards VTP advertisements (server to
client, client to client) but will not synchronize itself. It manages its own
VLAN database, which will not be shared with any other switch.

Q: What is Spanning Tree Protocol and root bridge election?

A: Spanning Tree Protocol (STP) is one of the most important
switching technologies to eliminate layer 2 switching loops. The root bridge
serves as an administrative point for all spanning-tree calculations to
determine which redundant links to block.

All switches send BPDUs (Bridge Protocol Data Unit) every 2
seconds from its ports which contain bridge-id, bridge-mac, cost,
port-priority, etc.

For root bridge selection, STP prefers lowest bridge-priority if
there is a tie in priority, then the lowest MAC address will determine which
bridge becomes the root. Lower priority is preferred compared to a higher. The
default bridge priority is 32768 and you can set it in multiples of 4096.

Q: What is the difference between PVST, PVST+ and RPVST?

A: Per VLAN Spanning Tree (PVST) is a Cisco proprietary
technology used to configure a separate spanning tree instance for each VLAN.
It supports ISL trunking encapsulation whereas PVST+ supports Dot1Q trunking
encapsulation.

Rapid PVST (RPVST) works the same as PVST, but their main
difference is fast convergence. RPVST skips the listening state during the
transition.

Q: Give a reason for selecting MST rather than PVST.

A: The main reason for selecting MST rather than PVST/STP is the
number of different VLANs involved. With 30 to 40 VLANs you can use PVST
without any concerns.

However, if there are 40 VLANs in a switch, it has to maintain
40 spanning tree databases (a separate database for each VLAN) and if you
decide to use MST, you need to provision some instances (logical grouping of
VLANs).

Let’s say you configure two instances, each with 20 VLANs. The
switch has to maintain only two spanning tree databases (a separate database
for each instance) then.

Q: What is EtherChannel and is it possible to achieve load
balancing using EtherChannels?

A: EtherChannel is a LAN port aggregation technology which allows
grouping of several physical Ethernet links to create one logical Ethernet link
for the purpose of providing fault-tolerance and high-speed links between
switches, routers and servers.

Yes, EtherChannel supports load balancing on the basis of
predefined hash algorithms but you cannot control the port that a particular
flow uses.
The hash algorithm cannot be configured or changed to load balance the traffic
among the ports in an EtherChannel.

Main hash algorithms are src_ip_addr | dest_ip_addr |
src_mac_addr | dest_mac_addr | src_port | dest_port} [dest_ip_addr |
dest_mac_addr | dest_port.

Q: What is DHCP, DHCP relay, and DHCP snooping?

A: Dynamic Host Configuration Protocol (DHCP) is a network
protocol that automatically assigns IP addresses to hosts with other related
configuration information such as the subnet mask and default gateway.

DHCP Relay is just a proxy that is able to receive a DHCP
request and resend it to the real DHCP server. It means a DHCP server is
installed at a remote location and your LAN gateway is acting as a DHCP relay
agent (proving the information of DHCP server using “ip helper address”
command).

DHCP snooping is a security mechanism which enables you to
configure a switch port connected to a DHCP server as a trusted port. The
trusted port is responsible for the reply DHCP requests. DHCP snooping is the
best solution to prevent man-in-the-middle DHCP attacks.

Q: What are the basic differences between HSRP and VRRP?

A: Both HSRP and VRRP are high availability protocols that
provide first hop redundancy.

HSRP

·
* Cisco proprietary

·
* 1 Active + 1 standby router and 1 or more listening routers

·
* Uses separate virtual IP addresses as gateway

·
* Hello timer is 3 seconds and hold-down timer is 10 seconds

·
* Preempt is disabled by default

·
* Multicast at 224.0.0.2 (ver1), multicast at 224.0.0.102
(ver2). Both versions use UDP port 1985

·
* HSRP (v2) supports IPv6

VRRP

·
* Open standard (IETF)

·
* 1 master and 1 or more backup routers

·
* Physical IP address can be used for Virtual IP

·
* Hello timer is 1 second and hold-down timer is 3 seconds

·
* Preempt is enabled by default

·
* Multicast at 224.0.0.18 – IP 112

·
* VRRP does not support IPv6

Network Engineer/Administrator (security) is a higher-level position,
often with “jr.” and “sr.” prefixes. The major responsibility of a network
engineer (security) is to determine “how to implement network security” in
routed LAN/WAN environments. They design and implement both the hardware and
software necessary technologies to secure computer network. They have
high-level technical skills in LAN/WAN security. The major responsibility of a
network admin (security) includes adding security software and hardware,
performance monitoring, troubleshooting, logging errors, backing up and
restoring data, and assigning permissions to users.

Network concepts:

·
* Data communication and transmission techniques

·
* Fundamentals of OSI & TCP/IP model

·
* Router’s basic operations (startup, nvram, flash/IOS backup
& recovery)

·
* IP Addressing and Summarization

·
* IP Routing : Basics of RIP , EIGRP , OSPF & BGP

Firewall

·
* NAT (object based)

·
* ACL (object based)

·
* Contexts

·
* Failover (Active-Standby & Active-Active)

·
* Transparent

·
* MPF (Modular Policy Framework)

VPN

·
* Site to Site

·
* SSL

·
* Get VPN

·
* Easy VPN

·
* DMVPN

·
Flex

Route-Filtering

·
* Access-lists

·
* Route-Maps

·
* Prefix-Lists

·
* Distribute-Lists

·
* Filter-lists

·
* Class-maps & Policy-maps

Network security

·
* AAA Server

·
* Dot 1x Authentication

·
* Ip SLA

Questions for an Interview of Network Security
Engineer/Administrator: All listed questions are very common and important and you
must be prepared with all of the following answers before facing any interview
for a Network Security position.

Q. What is a firewall?

Q. What is the difference between network gateway and a firewall?

Q. What is the difference between IPS and a firewall?

Q. What is a transparent firewall?

Q. What is packet filtering?

Q. Define stateful inspection?

Q. What is the Public Key Encryption?

Q. Define Digital Signatures

A: Digital signature is an attachment to an electronic message
used for security purposes. It is used to verify the authenticity of the
sender.

Q. What is Authorization?

Q. What is stateful failover?

Q. What is VPN and describe IPsec VPN

A: Virtual Private Network (VPN) creates a secure network
connection over a public network such as the internet.

IPsec VPN means VPN over IP Security allows two or more users to
communicate in a secure manner by authenticating and encrypting each IP packet
of a communication session.

Q. What is Site to Site and remote access VPN?

Q. How do you check the status of the tunnel’s phase 1 & 2 ?

A: Use following commands to check the status of tunnel
phases:

Phase 1 : show crypto isakmp and State : MM_ACTIVE

Phase 2 : show crypto ipsec sa

Note: if you have lot of tunnels and the output is confusing use
a ‘show crypto ipsec sa peer 12.12.12.12′ command instead.

Q. What is SSL VPN? How it is different from IPsec VPN?

IPsec is a dedicated point-to-point fixed VPN connection where
SSL VPNs provides anywhere connectivity without any configuration or special
software at remote site.

Q. What is GRE and why is it required?

A: Generic Routing Encapsulation (GRE) is a protocol that
encapsulates packets in order to route other protocols over IP networks.

GRE enables a wrapper to be placed around a packet during
transmission of the data. A receiving GRE removes the wrapper, enabling the
original packet to be processed by the receiving stack.

Advantages of GRE tunnels include the following:

·
* GRE tunnels connect discontinuous sub-networks.

·
* GRE tunnels allow VPNs across wide area networks (WANs).

·
* GRE tunnels encase multiple protocols over a single-protocol
backbone.

·
* GRE tunnels provide workarounds for networks with limited
hops.

Q. Firewalls work at what layer? Define firewall generations and
their roles.

A: Firewalls work at layer 3, 4 & 7. First generation
firewalls provide packet filtering and they generally operate at layer 3 (Network
Layer). Second generation firewalls operate up to the Transport layer (layer 4)
and records all connections passing through it and determines whether a packet
is the start of a new connection, a part of an existing connection, or not part
of any connection. Second generation firewall is mainly used for Stateful
Inspection.

Q. What is DoS attack? How can it be prevented?

Q. What is IP Spoofing?

Q. What are the security-levels in cisco ASA?

Q. What is AAA?

A: AAA stands for authentication, authorization and
accounting, used to control user’s rights to access network resources and to
keep track of the activity of users over a network. The current standard by
which devices or applications communicate with an AAA server is the Remote
Authentication Dial-In User Service (RADIUS).

Q. What is IPS? How does it work?

A: An Intrusion Prevention System (IPS) is a network
security/threat prevention technology that examines network traffic flows to
detect and prevent vulnerability exploits. An Intrusion Prevention System can
play a good role to protect against various network security attacks such as
brute force attacks, Denial of Service (DoS) attacks, and vulnerability
detection. Moreover, an IPS also ensures prevention against protocol exploits.

Intrusion Prevention System uses four types of approaches to
secure the network from intrusions which include:

·
* Signature-Based

·
* Anomaly-Based

·
* Policy-Based

·
* Protocol-Analysis-Based

Top Interview Questions for VoIP
Engineer/Administrators

NOTE: Click here to download additional potential interview questions.

Are you looking for job as a VoIP engineer/administrator? Or are
you thinking of leaving your current position for a new job as a VoIP engineer/administrator
with a new company in a Unified communication networking?

If you answered yes to either of those questions, this article
is for you.

A Network Engineer/Administrator (VoIP) position is a
higher-level position, often with a “junior” or “senior” prefix. The major
responsibility of a VoIP engineer is to design and implement both the hardware
and software technologies needed for a VoIP setup. They have to customize VoIP
networks as per the organization’s needs, such as adding software and hardware,
performance monitoring, troubleshooting, logging errors, backing up and
restoring data, assigning permissions to users, and helping users for VoIP
network issues.

Before facing any interview for a VoIP engineer position, make
sure that you have enough knowledge on the below technologies:

General Network concepts

·
* Fundamentals of OSI & TCP/IP model

·
* IP Addressing & Summarization

·
* Basics of routers and routing (EIGRP,OSPF,BGP)

·
* Basics of LAN Switching (VLANs, Inter-VLAN routing, STP)

·
* Network Services (Telnet, SSH, NTP, DHCP, Syslog)

VoIP Topics

·
* IP phone boot process

·
* Phone registration through CME (IOS based)

·
* CME features- call park, call pick-up, paging, intercom

·
* Understanding of clusters, ISDN configuration

·
* VoIP dial peers and POTS

·
* Cisco ip phone registration through CUCM (Manual/Auto/BAT)

·
* Understanding and Implementation of voice gateways
MGCP,H.323,SIP

·
* Signaling and Flow of voice gateways

·
* Call routing elements : route group, route list, SLRG

·
* Partition & CSS

·
* Media Recourses

·
* Integration of CUCM with CUC via SCCP & SIP

·
* Mobility : device/extension mobility, MUA, Single Number reach
(SNR)

·
* Survivable Remote Site Telephony (SRST)

·
* Call manager fall back

·
* Resource Reservation Protocol (RSVP)

·
* Automated Alternate Routing (AAR)

My Best Questions for an Interview for VoIP
Engineer/Administrators:
All of the
questions below are very common and must be prepared for before facing any
interview for the unified communication environment.

Q. What is VoIP?

A: Voice over Internet Protocol (VoIP) is the technology to
send your voice (analog data) over the internet (digital data) to an end user.
It enables users to use the Internet as the transmission medium for voice calls
at a very low cost.

Q. How does VoIP (voice over Internet protocol) work? What makes
it different from traditional phone service?

A: In VoIP, phone conversations are converted to packets that
flit all over the Internet or private networks, just like e-mails or Web pages,
though voice packets get priority status. The packets get reassembled and
converted to sound on the other end of the call but in traditional phone
service, a phone conversation is converted into electronic signals that
traverse an elaborate network of switches, in a dedicated circuit that lasts
the duration of a call.

Q. What are some disadvantages of using VoIP?

A: VoIP is far better than traditional telephony but it has
some drawbacks as listed below:

·
* Some VoIP services don’t work during power outages and the
service provider may not offer backup power.

·
* Not all VoIP services connect directly to emergency services
through 9-1-1.

·
* VoIP providers may or may not offer directory assistance/white
page listings.

Q. What basic set-up equipment is needed for VoIP?

A: For general VoIP set up we require the following things:

·
* Broadband connection

·
* VoIP phone

·
* Nexton soft-switches

·
* Router

·
* Audiocodec

·
* Astric server

Q. What is PVDM and what is the use of it?

A: PVDM stands for Packet Voice DSP (digital signal processor) Module and it enables Cisco Integrated
Services Routers to provide high-density voice connectivity, conferencing, and
transcoding capabilities in Cisco IP Communications solutions.

Q. What is VoIP gateway and explain the basic features of it?

A: A VoIP gateway works as a bridge between an IP network and
the PSTN. It converts analog telephony signals to digital.

VoIP gateways include the following features:

·
* Call routing, packet processing and control signalling
managementVoice and fax compression/decompressionExternal controller interfaces,
for example to a soft switch, billing system or network management system

Q. What is the difference between MGCP & H.323 Voice gateways?

MGCP

·
* Uses clear text for call controlUses a client-server
modelIdeally positioned for service providers (centrally located call
agents)Centralized management and control (Dial plan, etc.)Enhanced call
survivabilityBetter feature interaction with capabilities like Caller-IDSupport
of QSIG supplementary services with CCM

H.323

·
* Uses Abstract Syntax Notation 1 for call control messagesUses
a peer-to-peer modelScales well in an enterpriseFractional PRI supportCaller-ID
support on analog FXOMany more TDM interface types and
signallingGateway-resident applications like TCL and VXMLCAC network design
with H.323 GatekeepersNo release dependencies between GWs and CCMCall
preservation for SRST on PRIsNFAS support

Q. What is the difference between Transaction, Dialog and Session?

A: Transaction: A Transaction refers to a fundamental unit of message
exchange, between the SIP user agents.; It basically includes a
request-response cycle.

Dialog: A peer-to-peer relationship between two use agents. It is
usually created through generations of SUCCESSFUL final response.

Session: A Session refers to the exchange of media between two or more
endpoints.

Q. What you will do if you get a crackling sound on VoIP line
while talking?

A: Often we get this kind of issue with analog phones which
create a crackling sound when you talk, but is not common for VoIP provider or
internet connection as digital systems don’t generate sounds like this. It’s
only possible that it could be from the person on the other end who is also on
an analog telephone line but if this happens with different people then it’s
likely your phone. Try to replace the phone.

Q. What is SLRG & why do we use it?

A: SLRG (Standard Local Route Groups) eliminates the pairing
between the gateway and the Route Pattern, thus creating a more flexible method
of selecting a PSTN gateway.

Because it reduces the number of route patterns that need to be
created per country, a huge amount of administrative overhead can be saved,
especially for organizations with a large number of sites.

Q. What is the basic difference between VoIP and POTS (Plain old
telephone systems) dial-peers?

A: VoIP dial peers route calls to other VoIP systems via IP
protocol where POTS dial peers route calls to legacy PBX systems via local
ports which can be analog (like FXS, FXO) or digital (like E1/T).

Q. What is sip trunk and what are the basic benefits of using SIP
trunk?

A: SIP Trunk is a voice call connection placed over your
Internet connection. This VoIP “trunk” (or phone line) connects to a provider
who routes your calls through their gateway and usually has very reasonably
lower rates on long distance calls, international calls and in-bound toll free
calls.

Additionally, SIP trunks can carry instant messages, multimedia
conferences, user presence information, and Enhanced 9-1-1 (E9-1-1) emergency
calls.

·
* Eliminate BRI and PRI subscription fees because SIP trunk
connected directly to an Internet telephony service provider

·
* Eliminate IP-PSTN gateways (or even your entire PBX)

·
* Low cost long distance calls, international calls, etc.

·
* Expansion of lines is dependent on bandwidth, which can easily
be increased if needed. It means that with SIP trunking you don’t need to buy
lines in blocks of 24 or 32. Instead, you can buy the bandwidth you need in
smaller increments.

Q. What is the difference between E1 and T1 Link? In which country
are we using t E1 and T1 for digital transmission?

A: The main difference between E1 and T1 is the data rate. T1
has a data rate of 1.544 mbps and E1 has a data rate of 2.048 mbps.

Other differences between T1 and E1 lies in the number of
channels (E1-32 Channel and T1-24 channels) but speed (64 kbps) remains the
same for both links: may be for inter – connection between the E1 and T1 lines.
This is interconnected because it is used for international connectivity
purposes.

T1 is used mainly in the United States, Canada, Hong Kong and
Japan. E1 is mostly used in Europe.

Q. How many channels are in E1 and T1 link? What is the
operational bandwidth of each channel in each link?

A: E1 link contains 32 channels where T1 link contains 24
digital channels and each channel of both T1/E1 gives you 64 kbps bandwidth.

An E1 link consists of 30B channels and 1D channel and each
channel has 64k Bw.

So for E1 – you get 30*64 = 1920kbps

A T1 link consists of 23B channels and a D channel and each
channel has 64k Bw. So for T1 – you get 23*64 = 1472kbps

Q. What is the signalling and what is the difference between CAS
and CSS?

A: Signalling is a way of information exchange to
establishment and control of a telecommunication circuit and the management of
the network.

Common channel signalling (CAS) uses a dedicated channel for the
signalling where Channel Associated Signalling (CAS) conveys signalling
information relating to multiple bearer channels. These bearer channels
therefore have their signalling channel in common.

CCS with E1 =30 B channels and 1 D channel

CCS with T1 = 23 B channels and 1 D channel

CAS with E1 = 31 B Channels

CAS with T1 = 24 B Channels

B=Bearer channels responsible for carrying voice signal

D=Data channel responsible for signalling control

Q. What are the basic differences between G711 and G729 codec?

A: G729 is a compressed audio codec with better tolerance for
packet loss and jitter than G711. G729 uses 33 Kbps of bandwidth whereas G711
uses 87 Kbps. G729 is compressed but still sounds very good in poor network but
G711 sounds better only with good network conditions.

Q. Can we configure trunking between Cisco and Avaya PBX?

A: QSIG PRI trunking configuration can be used to establish
trunking between Cisco and Avaya PBX.
Q signalling (QSIG), a protocol for Integrated Services Digital Network (ISDN)
communications based on the Q.931 standard, is used for signalling between
digital PBXs.

The questions above are very tricky and important from the
standpoint of clearing any interview for a VoIP network engineer/administrator
position. It is not possible for anyone to explain all kinds of questions, but
you can get more frequently asked interview questions for VoIP Network
Engineering Jobs from the download link posted here. If you find any difficulty in answering any questions, then you
can write me @ Comment section.

Collision Domain

A term collision is
described as an event that usually happens on an Ethernet network when we use a
“Shared Media” to connect the devices in an Ethenrnet network. A
“Shared Media” is a type of connecting media which is used to connect
different network devices, where every device share the same media. Example: 1)
Ethernet Hubs, 2)
Bus Topology

In a “Shared
Media” there are no separate channels for sending and recieving the data
signals, but only one channel to send and recieve the data signals.

We call the media as shared
media when the devices are connected together using Bus topology, or
by using an Ethernet Hub.
Both are half-duplex, means that the devices can Send OR Recieve data signals
at same time. Sending and recieving data signals at same time is not supported.

Collisions will happen in an
Ethernet Network when two devices simultaneously try to send data on the Shared
Media, since Shared Media is half-duplex and sending and recieving is not
supported at same time. Please refer CSMA/CD to
learn how Ethernet avoid Collision.

Collisions are a normal part
of life in an Ethernet network when Ethernet operates in Half-duplex and under
most circumstances should not be considered as a problem.

A Collision
Domain is any network segment in which collisions can happen (usually in
Ethernet networks). In other words, a Collision Domain consists of all the
devices connected using a Shared Media (Bus Topolgy or
using Ethernet Hubs)
where a Collision can happen between any device at any time.

Collision Domain

For Example, if
“Computer A” send a data signal to “Computer X” and
“Computer B” send a data signal to “Computer Y”, at same
instance, a Collision will happen.

As the number of devices in
a collision domain increases, chances of collisions are also more. If there is
more traffic in a collision domain, the chances of collisions are also more.
More collisions will normally happen with a large number of network devices in
a Collision domain.

Increased collisions will
result in low quality network where hosts spending more and more time for
packet retransmission and packet processing. Usually switches are used to
segment (divide) a big Collision domain to many small collision domains. Each
port of an Ethernet Switch is operating in a separate Collision domain.

In other words, Collision
cannot happen between two devices which are connected to different ports of a
Switch.

No need to worry much about
collision and related network problems now because we are not using Network
Hubs to connect our devices. Ethernet Network Hubs are
replaced with Ethernet Network
Switches long way back.

Broadcast Domain

Broadcast is a type of
communication, where the sending device send a single copy of data and that
copy of data will be delivered to every device in the network segment. Brodcast
is a required type of communication and we cannot avoid Broadcasts, because
many protocols (Example: ARP and
DHCP)
and applications are dependent on Broadcast to function.

A Broadcast
Domain consists of all the devices that will receive any broadcast packet
originating from any device within the network segment.

Broadcast Domain

In above picture,
“Computer A” is sending a broadcast and switch will forward it to
every ports and all the switchs will get a copy of broadcast packet. Every
switch will flood the broadcast packet to all the ports. Router also will get a
copy of broadcast packet, but the Router will not forward the packet to the
next network segment.

As the number of devices in
the Broadcast Domain increases, number of Broadcasts also increases and the
quality of the network will come down because of the following reasons.

1)
Decrease in available Bandwidth: Large number of Broadcasts
will reduce the available bandwidth of network links for normal traffic because
the broadcast traffic is forwarded to all the ports in a switch.

2)
Decrease in processing power of computers:
Since the computers need to process all the broadcast packets it recieve, a
portion of the computer CPU power is spent on processing the broadcast packets.
Normally a Broadcast packet is relevent to a particular computer and for other
computers that broadcast packet is irrelevant (For example, DHCPDISCOVER
message is relevent only for a DHCP Server. For other computers DHCPDISCOVER is
irrelevant and they will drop the packet after processing). This will reduce
the processing power of computers in a Broadcast domain.

By design, Routers will not
allow broadcasts from one of its connected network segment to cross the router
and reach another network segment. The primary function of a Router is to
segment (divide) a big broadcast domain in to multiple smaller broadcast
domains.

Difference
between Static and Dynamic IP.

Static IP is also called as
permanent address assigned to each device in a network, whereas Dynamic IP, a
temporary address assigned to the device via DHCP software. IP address assigned
to your service by your cable or DSL Internet provider is typically dynamic IP.
In routers and operating systems, the default configuration for clients is
dynamic IP

What is the
difference between public and private IP?

A public IP address allows
equipment accessible to everyone on the internet. A private IP address is for
private use within the network and allows many more PCs to be connected. If you
are using a private IP and wants VOIP, you need to change to a public IP
address.

What is
Network Address Translation?

Network Address Translation acts
as an agent between the Internet and a local network. It is a dynamic method
which is used to minimize Internet connectivity needs. Network address
translation describes the rewriting of the Internet Protocol (IP) addresses of
data packets so that multiple transmissions require only one IP address.

Define IP
multicast.

IP multicast technology reduces
traffic by sending stream of information to many recipients at one go. Video
conferencing, stock quotas are the examples based on IP multicast.

What is
subneting?

Subnet adds one level to the way
IP address is represented. It logically organizes the network. For instance, it
can logically group computers belongs to the finance department.

Define
Address Resolution Protocol.

Address Resolution Protocol ARP,
is responsible for mapping an IP address to its corresponding physical network
address. It is mostly seen on Ethernet network.

Explain
Maximum Transfer Unit, MTU.

MTU specifies the largest amount
of data that can be transferred across a network.

What is
Routing Protocol?

Routing protocol is the way to
send routing information between any routers in an autonomous system.

When a source sends a packet to a
destination, this packet has a specific path or route it follows. Different
routing protocols are used to find the shortest path to the destination. The
protocols maintain routing tables. Routing tables consist of a set of rules
used to determine where these packets will travel. When a packet is received, a
network device examines the packet and matches it to the routing table entry
providing the best match for its destination. The packet keeps hopping until it
reaches its destination

Explain the
structure and use of internet addresses.

Each IP address is 32 bit long.
In human language the IP addresses are written in dotted decimal notation.
These are then converted to binary by the computer. Each IP address has two
parts: Network identifier or a network ID and host ID. The current internet
protocol standard is IPV4. The IP addresses are divided into three classes: a
class A network, a class B network, and a class C network. Class A being the
largest. The four digit numbers in an IPV4 address, each network of class A
will have different first number, and then its network will be addressed by the
rest of the three numbers, or three bytes. The IP addresses identify a machine
to deliver packets and load web pages.

Explain how
names are translated (resolved) into IP address.

Domain Name server or DNS is used
to resolve names into IP addresses. When a web address is entered into the
browser, the DNS client sends a request to the DNS server to find the
corresponding IP address for the name. The DNS server receives this request and
searches for the corresponding IP address in the database. If at this point the
resolution fails, this server sends this request to the parent server. The
request keeps going up the hierarchy to the parent servers or the closest
authoritative of the DNS server to resolve the address. If the request times
out an error is retuned to the client. If the server is able to resolve the
name requested, it passes the information back to the client. The next request
sent by the client is to request for a web page for the IP address.

Describe the
basics of internet routing.

Define
broadcast domain.

It is a logical area in a
computer network where any computer connected to the network can directly
transmit to any other computer in the domain without having to go through a
routing device.

Bridge vs
switch

A bridge connects two different
LAN networks. A switch is something like you can connect many computers to a
switch and then one computer can connect to another through the switch. Switch
is a unicast one to one connection.

What is a
Router?

A router is a device or sometimes
a software in a computer which decides the next network point to which a packet
should be forwarded to reach its destination on Internet. It is usually
included as part of the network switch and is located at a gateway, including
each point-of-presence on the Internet. The router is connected to at least two
networks and determines which way to send each information packet based on its
understanding of the state of the networks it is connected to.

Define
gateway

A gateway is a network point that
provides entrance into another network. On the Internet, a node or stopping
point can be either a gateway node or a host (end-point) node. Both the
computers of Internet users and the computers that serve pages to users are
host nodes. The computers that control traffic within your company’s network or
at your local Internet service provider (ISP) are gateway nodes.

What is
firewall?

A firewall is a hardware or
software installed to provide security to the private networks connected to the
internet. They can be implemented in both hardware and software, or a
combination of both. All data entering or leaving the Intranet passes through
the firewall which allows only the data meeting the administrators’ rules to
pass through it.

What are the
types of firewalls?

Packet Filtering Firewall:
This type of Firewall detects packets and block unnecessary packets and makes
network traffic release.

Screening Router
Firewalls:
It’s a software base firewall available in Router provides only light
filtering.

Computer-based Firewall:
It’s a firewall stored in server with an existing Operating System like Windows
and UNIX.

Hardware base Firewall:
Its device like box allows strong security from public network. Mostly used by
big networks.

Proxy Server:
Proxy server allows all clients to access Internet with different access
limits. Proxy server has its own firewall which filters the all packet from web
server.

What is Data
encryption?

Data encryption ensures data
safety and very important for confidential or critical data. It protect data
from being read, altered or forged while transmission.

What is the
Public Key Encryption?

Public key encryption use public
and private key for encryption and decryption. In this mechanism, public key is
used to encrypt messages and only the corresponding private key can be used to
decrypt them. To encrypt a message, a sender has to know recipient’s public
key.

Define
Digital Signatures.

Digital signature is an
attachment to an electronic message used for security purpose. It is used to
verify the authenticity of the sender.

What is
Ethernet technology?

Ethernet technology is a high
speed broadcast bus technology. In this type, all the station shares a single
ether channel and receives every single transmitted signal.

What is CSMA
and CD concept?

In CSDA (carrier sense multiple
access), presence of any digital signal in a network is checked before
transmission. Data transmission occurs only when no signal is sensed.

CD, Collision detection is
responsible for monitoring carrier in order to avoid signal jam.

What is
NetBIOS protocol?

NetBIOS (Network Basic
Input/Output System) Protocol allows applications on separate computers to
communicate over a LAN. It runs over TCP/IP giving each computer in the network
a NetBIOS name and IP address. E.g. It can be used for computers running
Windows 2000 (or before) to join a computer network running Windows 2000 (or
later).

What is IGMP
protocol?

Internet Group Management
Protocol, allows internet hosts to multicast. i.e. to send messages to a group
of computers. There may be a group of internet hosts interested to multicast.
IGMP allows router to determine which host groups have members on a given
network segment. It helps to establish group memberships. It is commonly used
for streamlining videos and gaming. The protocol can be implemented both as a
host side and router side. The host side is responsible to notify its
membership in a group. The notification is made to a local router. This local
router (router side) in turn sends out queries.

What is TCP
/ IP protocol?

Transmission Control Protocol /
Internet Protocol: – It is a family of protocols used for communication and
connection between hosts on the internet. It is the most widely used standard
for transmitting data over the internet. The four layers in the protocol are
(from bottom to top):- Physical layer, Data link layer, Network layer,
transport layer and application layer, also called as the OSI model. In TCP/IP
, IP is responsible for forwarding packets while TCP ensures the correct
delivery of data from client to server. TCP detects loss of data as well.

What is HTTP
(Hypertext Transfer Protocol)?

HTTP or Hyper Text Transfer
Protocol is provides a set of rules to transfer files, videos, images over the
world wide web. When the web browser is opened, a HTTP request call is made. A
web server contains a HTTP daemon. This daemon is used to wait for HTTP
requests and handle them when they arrive. The web browser from where HTTP
requests are made is called as a client. These requests are sent to the server.
It uses a reserved port no 80.

What is NNTP
(Network News Transfer Protocol)?

NNTP or Network News Transfer
Protocol is used to manage the notes posted on Unset newsgroup (a collection of
posted notes on a subject posted by different users). NNTP servers are
responsible for managing Usenet newsgroup collected globally. A NTTP client is
a part of the web browser also called as a news reader. It uses a reserver port
no 119.

What is POP3
(Post Office Protocol 3)?

POP3 or Post Office Box 3 is used
fro receiving emails. It is a client server protocol which holds the email.
Once the email is downloaded from the server, POP3 deletes it from the server.
Ordinal numbers are used to identify specific messages.

What is SNMP
(Simple Network Management Protocol)?

SNMP or Simple Network Management
Protocol is typically used for managing the network. Managing the network
includes managing the nodes present in the network. These nodes may be server,
routers, bridges and hubs. SNMP agents are used to achieve this. Managing the
network is essential because it helps to monitor network performance, detect
network faults or failures, audit network usage etc. the SNMP messages like
TRAP, GET or SET may be invoked by network elements or network management
system.

What is Routing
Protocols?

Routing protocols are used to
assist in achieving the basic purpose of routing. They specify the routers the
method to communicate with each other. They help the routers select the best
possible path between nodes. There are different types of protocols such as
link-state routing protocols, path vector protocols and distance vector routing
protocols. These protocols prevent routing loops to form or break if formed
already. They help to decide preferred routes from a sequence of hop costs..

What is
Distance Vector Routing Protocols?

The main goal of Distance Vector
Routing Protocols Is to find out the best path for he data packet to reach the
destination. Distance here could be the hops. The three different types of
Distance Vector routing protocols include:- Routing Information Protocol (RIP
v1 and v2) and Interior Gateway Routing Protocol. The protocol is easy to
manage however not well scalable.

The Distance Vector protocol
initially prepares a Routing table which is shared with other routers. This
routing table is shared between routers present in the same network. A new
routing table is prepared when some new information is received from some other
router. Now, the bad routing paths are removed keeping only the smallest hop
paths. This new table is then communicated to other routers.

Explain
Transmission Control Protocol, TCP

TCP ensures reliable and end to
end delivery of segments of information. Segments are acknowledged to the
source when received by the destination. Data is broken up into segments and
sequenced properly before transmission. This arrangement of segments allows
destination to trace lost data in transmission.

What is TCP
protocol?

Transmission control Protocol is
used to establish communication between nodes or networks and exchange data
packets. It guarantees delivery of data packets in the order they were sent.
Hence it is most commonly used in all applications that require guaranteed
delivery of data. It can handle both timeouts (if packets were delayed) and
retransmission (if packets were lost). The stream of data is transmitted in
segments. The segment header is 32 bit. it is a connectionless communication
protocol at the third level (network) of the OSI model.

TCP vs. UDP.

TCP guarantees the delivery of
data. UDP on the other hand, does not guarantee delivery of data. TCP delivers
messages in the order they were sent. UDP has no ordering mechanisms. In TCP
data is sent as a stream while UDP sends data as individual packets. UDP is
faster than TCP. TCP is a connection oriented protocol while UDP is
connectionless.

Explain User
Datagram Protocol, UDP.

The UDP is a connectionless,
unreliable service. UDP messages can be lost and duplicated.

What is UDP
protocol?

User Data Protocol is a
communication protocol. It is normally used as an alternative for TCP/IP.
However there are a number of differences between them. UDP does not divide
data into packets. Also, UDP does not send data packets in sequence. Hence, the
application program must ensure the sequencing. UDP uses port numbers to
distinguish user requests. It also has a checksum capability to verify the
data.

TCP vs. UDP.

What is TCP
windowing concept?

TCP windowing concept is
primarily used to avoid congestion in the traffic. It controls the amount of
unacknowledged data a sender can send before it gets an acknowledgement back
from the receiver that it has received it.

What is
Trusted and Untrusted Networks?

Trusted networks: Such Networks allow data to be transferred
transparently. The machines using a trusted network are usually administered by
an Administrator to ensure that private and secured data is not leaked. Access
to this network is limited. Computers using trusted networks are more secured
and confidential because of strong firewalls.

Untrusted networks: Such networks are usually administered by the
owners. They can allow improper access to sensitive or personal data. These
machines are usually separate. Such machines could me more prone to
attacks.

What are the different types of VPN?

Remote Access VPN:- Also called as Virtual Private dial-up network (VPDN) is mainly
used in scenarios where remote access to a network becomes essential. Remote
access VPN allows data to be accessed between a company’s private network and
remote users through a third party service provider; Enterprise service
provider. E.g Sales team is usually present over the globe. Using Remote access
VPN, the sales updates can be made.

Site to Site VPN – Intranet based: This type of VPN can be used when multiple
Remote locations are present and can be made to join to a single network.
Machines present on these remote locations work as if they are working on a
single network.

Site to Site VPN – Extranet based: This type of VPN can be used when several
different companies need to work in a shared environment. E.g. Distributors and
service companies. This network is more manageable and reliable.

What are the different authentication methods used in VPNs?

The authentication
method uses an authentication protocol. The methods are:

EAP authentication
method: Extensible authentication protocol
authenticates remote access connection. The authentication mechanism is decided
between the remote VPN client and authenticator (ISA). The mechanism is typical
in which authenticator requests for authentication information and the
responses are given by the remote VPN client.

MS Chap Authentication
method: Microsoft Challenge Handshake
Authentication Protocol (MS-CHAP) starts with the authenticator (Remote access
server) challenge. The challenge to the remote access client sends a session
identifier and challenge string. The client in response sends the nonreversible
encryption of the string, the identifier and password. Authenticator checks the
credentials and grants access on a successful authentication.

Unencrypted passwords
(PAP):- Uses plain text passwords. Does not involve
encryption. Used for less secure clients.

Shiva Password
Authentication Protocol (SPAP):- It is a password
authentication protocol. It is less secure as the same user password is always
sent in the same reversibly encrypted form

What is
Tunneling?

Tunneling is a mechanism provided
to transfer data securely between two networks. The data is split into smaller
packets and passed through the tunnel. The data passing through the tunnel has
3 layers of encryption. The data is encapsulated. Tunneling can be approached
by Point to Point tunneling protocol.

What are
voluntary and compulsory tunnels?

Voluntary Tunneling
Users computer is an end point of the tunnel and acts as tunnel client. Here
the client or user issues a request to configure and create a voluntary tunnel.
They require a dial up or LAN connection. Example of dial up connection is
internet at home where a call is made to the ISP and connection is obtained.

Compulsory tunneling
In compulsory tunneling, instead of the user a vpn remote access server
configures and creates a tunnel. Hence, the end point is the Remote sever not
the user.

Explain
static and dynamic tunnels.

Tunnels that are created manually
are static tunnels. Tunnels that are auto discovered are dynamic tunnels. In
dynamic tunneling, tcp connections can be checked dynamically. If no
connections exist that are routed through the tunnel, a check for more suitable
gateway can be done. Static tunneling may at times require dedicated
equipments.

Explain the
importance of increasing and decreasing subnet bits.

Adding 1’s as a bit means
increasing the subnets and decreasing the hosts. Removing or decreasing 1’s
means decreasing subnets and increasing hosts. Hence by increasing or
decreasing the subnet architecture can be decided as per needs.

Why do we
need a subnet mask?

A subnet mask allows
identification of host part and network part of an IP address. Subnet mask can
be used to find if an IP address is present on a subnet or not.

What is
RTP?

Real-Time Transfer Protocol lays
a standard or a way to transfer or manage real time data over a network. It
does not guarantee the delivery of data or provide any quality of service.
However it helps to manage the data. Which means that RTP can be used deliver
the necessary data to the application to make sure it can put the received
packets in the correct order Real time data examples could be audio and
video.

What is RTP
Multiplexing?

RTP multiplexing allows multiple
media flows within a single RTP data payload between two points. This means
that it can be used to carry multiple streams of data in one RTP packet. RTP
multiplexing will reduce the bandwidth used. RTP multiplexing will also
increase scalability.

Explain the
use of RTP and RTCP protocols.

Use of RTP and RTCP:-

1. RTP can be used to transfer
Real time data like voice packets.
2. RTP can be used with RTCP which makes it possible to monitor data.
3. Packet loss can be detected by RTP using Sequence number

RTCP provides Qos feedback :-
Packets lost, round trip time.

Describe the
format of RTP and RTCP packets.

The 32 bits of RTP packet format
is as follows:- (L to R)

Bit 0-1:- Indicates version,
currently 2
Bit 2:- P- indicates padding bytes
Bit 3:- X- Indicates presence of extension header
Bit 4-7:- CC- Contains number of CSRC identifiers that follows the header
Bit 8:- M- Current data has some special relevance (if set)
Bit 9-15:- PT- Indicates format of payload
Bit 16-31:- Sequence number
Timestamp: – 32bits – time stamp of packet
SSRC- Synchronization source identifier uniquely identifies the source of a
stream.
CSRC -Contributing source IDs enumerate contributing sources to a stream which
has been generated from multiple sources
Extension header: – first 32 bit word contains profile specific identifier and
length specifier

The 32 bits of RTCP header
format is as follows:- (L to R)
Bit 0-1:- Indicates version, currently 2
Bit 2:- P- indicates padding bytes
Bit 3 to 7:- Count of number of reception report blocks
Bit 8 to 15:- Type: – Determined RTCP packet type. Type can take values from 0
to 255
16 to 31:- Length- Length of RTCP packet – 1
SR: – Sender Report for transmission and reception from active senders
RR: – Receiver report for reception from in active senders
SDES: – Source description items
BYE- indicates end of participation
APP: – Application specific functions

Describe how
the multicast protocol works.

Multicast protocol or Internet
protocol delivers a singles message to multiple machines. One packet from the
source is replicated and sent to the destination. Every multicast message
requires a multi case group. The group defines the addresses which will receive
the message. The group is defined by the class D address. Different routing
protocols are used to find the multicast groups and build routes for them.
Distance Vector Multicast protocol is one of them. The receiver, to whom the
multicast packet is sent to, needs to ‘join’ the group. Joining the group is
enabled and managed by IGMP. Multicast routers are used to transmit the
messages from one network to another.

Describe how
to control the scope of multicast transmissions.

Controlling the scope of
multicast transmission restricts the range of group members. TTL (Time To Live)
is one of the mechanisms to limit the scope. If the TTL value is small, packets
would only be multicast to smaller distance destinations. More the value of
TTL, more would be the scope of transmission to a larger number of machines.
Administrative scoping is another mechanism. In this, transmission is
restricted to a specific address space of an organization or a site.

Explain why use Multicasting.

When the same message or packet
needs to be sent to multiple destinations, multicasting is used.
Within campus and offices,
using multicasting file distribution can be done.
System messages, news and
videos can be sent at the same time.
More commonly used for audio
and video streaming.

What is a
socket?

What are
Sockets? How do Sockets Work?

A socket is used to connect an
application to a network protocol. A socket enables communication between a
client and a server. The communication is started when the client is assigned a
local port number, and binds a socket to it. The client writes on the socket
and gets information from server by reading it. The Socket class is used to
communicate. It provides rich set of methods for both asynchronous and synchronous
data transfer. ConnectAsynch is used to start an asynchronous connection.
SendAsynch and ReceiveAsynch are used to send and receive data. Shutdown and
close methods are used to shutdown and close the sockets.

Datagram vs.
stream.

Stream can be considered as a
pipe that allows full duplex connection. A datagram or a packet on the other
hand, has a source and a destination. There is no connection. Stream is like a
communication channel while datagram is completely self contained. Streams
provide a reliable and sequenced communication. Datagram’s on the other hand
are unreliable and no sequence maintained.

What is a
stream socket?

A stream socket provides two way
communications between a client and server. This communication is reliable and
sequenced. Stream sockets are above TCP to run across any networks. They
provide unduplicated flow of data and have well established mechanism for
creating and destroying connections and for detecting errors.

What is SSL?

SSL is Secured Socket Layer. SSL
is used to establish a secured and an encrypted connection between a server and
the browser. SSL is most commonly seen in payment and banking web sites. To
create a SSL connection, a SSL certificate needs to be created. If the website
has a SSL certificate installed, a small icon is displayed in the tool bar to
make customers confident that the site is secured.

What are the two important TCP Socket classes? Explain them

The two most important
socket Classes are:

Socket Class: The Socket class provides enriched methods and properties
for network communications. It allows both synchronous and asynchronous data
transfer. Shutdown method should be used to end the Socket once the data
transfer is complete. Using SetSocketOption the socket can be configured.
Declaration:

Public Class Socket _
Implements IDisposable

Server Socket Class: The server Socket class is used to implement server sockets.
Server sockets are used to respond to requests received over the network.

What are the advantages and disadvantages of Java Sockets?

Advantages:

Flexible and powerful.
Cause low network traffic if
efficiently used.
Only updated information can be
sent.

Disadvantages:

The Java applets can establish
communication only with the machine requested and not with any other
machine on the network.
Sockets allow only raw data to
be sent. This means that both client and server need to have mechanisms to
interpret the data.

What is
meant by Symmentric Multiprocessing (SMP)?

Symmetric Multiprocessing allows
any processor to do work of another processor. SMP allows multiple processors
to process programs that are a part of common OS and memory. Most common
example of SMP is OLTP where many users access the same database in a
relatively simple set of transactions. SMP efficiently balances the workload of
the processors.

What are
TP-Lite and TP-Heavy Monitors?

TP – Lite is an integration of TP
Monitor functions in a database engine. TP-Heavy Monitor allows the machine to
initiate some complex multi server transactions. TP Heavy monitors support
client server architecture.

What is
Distance Vector Routing Protocols?

What is POP3
(Post Office Protocol 3)?

What is NNTP
(Network News Transfer Protocol)?

What is HTTP
(Hypertext Transfer Protocol)?

What is IGMP
protocol?

Define
gateway

Explain how
names are translated (resolved) into IP address.

Explain the
structure and use of internet addresses.

Each IP address is 32 bit long.
In human language the IP addresses are written in dotted decimal notation.
These are then converted to binary by the computer. Each IP address has two
parts: Network identifier or a network ID and host ID. The current internet
protocol standard is IPV4. The IP addresses are divided into three classes: a class
A network, a class B network, and a class C network. Class A being the largest.
The four digit numbers in an IPV4 address, each network of class A will have
different first number, and then its network will be addressed by the rest of
the three numbers, or three bytes. The IP addresses identify a machine to
deliver packets and load web pages.

Define IP
multicast.

IP multicast technology reduces
traffic by sending stream of information to many recipients at one go. Video
conferencing, stock quotas are the examples based on IP multicast.

What is
Network Address Translation?

Network Address Translation acts
as an agent between the Internet and a local network. It is a dynamic method
which is used to minimize Internet connectivity needs. Network address translation
describes the rewriting of the Internet Protocol (IP) addresses of data packets
so that multiple transmissions require only one IP address.

What is the
difference between public and private IP?

How would
you define IP address?

IP address or Internet Protocol
address is the address of a device attached to an IP network (TCP/IP network).
It is a must for every client, server and network device to have a unique IP
address for each network connection (network interface). Every IP packet contains
a source IP address and a destination IP address. As a device moves from one
network to another, its IP address changes.

Computers using the TCP/IP for
communication are uniquely identified by a 32 bit address called as an IP
address. The routers use the IP address information to forward the packet to
the destination computer.

IP addresses are categorized as:

Private address: these
IP addresses are used exclusively within a private network and not for public
to see.

Public Address: these
are registered IP addresses used for public.

Each IP address has a network
address and a host address. IP addresses are expressed in four sets of three
numbers, separated with dots. Each set is called as an octet because when
converted to binary; it denotes eight binary.

MAC vs. IP
Addressing

Whereas MAC addressing works at
the data link layer, IP addressing functions at the network layer (layer 3).
It’s a slight oversimplification, but one can think of IP addressing as
supporting the software implementation and MAC addresses as supporting the
hardware implementation of the network stack. The MAC address generally remains
fixed and follows the network device, but the IP address changes as the network
device moves from one network to another.

Define
Telnet

Telnet is the main Internet
protocol for creating a connection to a remote server.

Define DNS

The DNS translates Internet
domain and host names to IP addresses. DNS automatically converts the names we
type in our Web browser address bar to the IP addresses of Web servers hosting
those sites. DNS implements a distributed database to store this name and
address information for all public hosts on the Internet.

What
is Application layer?

The application layer is located
at the top of the TCP/IP protocol layers. This one contains the network
applications which make it possible to communicate using the lower layers. The
software in this layer therefore communicates using one of the two protocols of
the layer below (the transport layer), i.e. TCP or UDP. In computer networking,
an application layer firewall is a firewall operating at the application layer
of a protocol stack.[1] Generally it is a host using various forms of proxy
servers to proxy traffic instead of routing it. As it works on the application
layer, it may inspect the contents of the traffic, blocking what the firewall
administrator views as inappropriate content, such as certain websites,
viruses, and attempts to exploit known logical flaws in client software, and so
forth. An application layer firewall does not route traffic on the network
layer. All traffic stops at the firewall which may initiate its own connections
if the traffic satisfies the rules.

Explain the
core naming mechanism, Domain Name System (DNS).

A Domain Name system is used to
convert the names of the website on the internet to IP addresses. The domain
names for each IP addresses are stored in a database that is distributed across
different servers. A domain name space consists of a tree of domain names. The
tree has zones. Zones consist of a collection of connected nodes. These nodes
are served by a name server. A domain name is usually in the form of
mydomain.com. Here, .com is the top level domain. Where as mydomain is the sub domain or
subdivision. A host name is a domain name that has one or more IP addresses
associated with it.

Explain the
functionality of PING.

Ping Is particularly used to
check if the system is in network or not. It also gives packet lost
information. In windows ping command is written as ping ip_address. The output
returns the data packets information. The number of packets sent, received and
lost is returned by PING

What is
multicasting?

Multicasting allows a single
message to be sent to a group of recipients. Emailing, teleconferencing, are
examples of multicasting. It uses the network infrastructure and standards to
send messages.

Explain IP,
TCP and UDP.

TCP – Transmission control Protocol is used to
establish communication between nodes or networks and exchange data packets. It
guarantees delivery of data packets in the order they were sent. Hence it is
most commonly used in all applications that require guaranteed delivery of
data. It can handle both timeouts (if packets were delayed) and retransmission
(if packets were lost). The stream of data is transmitted in segments. The
segment header is 32 bit. it is a connectionless communication protocol at the
third level (network) of the OSI model.

IP – Internet protocol is used for transmission
of data over the internet. IP uses IP addresses to identity each machine
uniquely. Message is sent using small packets. The packet contains both the
sender and receivers address. IP does not guarantee the delivery in the same
order as sent. This is because the packets are sent via different routes. It is
a connectionless communication protocol at the third level (network) of the OSI
model.

UDP – User Data Protocol is a communication
protocol. It is normally used as an alternative for TCP/IP. However there are a
number of differences between them. UDP does not divide data into packets.
Also, UDP does not send data packets in sequence. Hence, the application
program must ensure the sequencing. UDP uses port numbers to distinguish user
requests. It also has a checksum capability to verify the data.

What are network topologies? Explain Ring, Bus and Star
topology.

A network topology
describes the layout of a network. It describes how different nodes and
elements are connected to each other. Different types of topology:

a. Ring:-

All nodes connected with
another in a loop.
Each device is connected to one
or more another device on either side.

b. Bus

All nodes connected to a
central and a common cable called as a back bone.
In bus topology, the server is
at one end and the clients are connected at different positions across the
network.
Easy to manage and install.
If the backbone fails, the
entire communication fails.

c. Star

All nodes connected to a
central hub.
The communication between the
nodes is through the hub.
Relative requires more cables
as compared to BUS. However if any node fails, it wont affect the entire
LAN.

What is a
network? What are the different kinds of network? Explain them

A network is a group of computers
or nodes connected together. They are connected with each other by
communication paths.

Types of Networks:

LAN – Local Area Network connects a group of
nodes covering a small physical area. LAN’s are most commonly seen in offices,
building etc. LAN’s enable higher transfer rate of data, smaller coverage of
area and hence less wiring.

WAN – Wide Area Network connects a group of nodes
covering a wide area. WAN typically connects and allow communication between
regions or national boundaries. The most common example of WAN is internet.

VPN – Virtual Private Network connects or links
nodes in some larger area by open connections or virtual circuits in some
larger network (e.g., the Internet) instead of by physical wires. It is used
for secure communication through the public internet. VPN alone may not support
explicit security features, such as authentication or content encryption.

Intranet – It is a set of networks under the control
of a single administrative person. It can be considered as an internal network
of an organization. If it is large, web servers are used to provide information
to the users.

Extranet – It is a network that restricts itself
within a single organization. It can be categorized as WAN, MAN etc. however;
it cannot have a single LAN. It must have a connection (at least one) with
external network.

Explain the
7 Layers of OSI.

Layer 1: Physical layer
It represents all the electrical and physical specifications for
devices.

Layer 2: Data link layer
It provides the functional and procedural means to transfer data between
network entities and to detect and possibly correct errors that may occur in
the Physical layer.

Layer 3: Network layer
The Network layer provides the functional and procedural means of transferring
variable length data sequences from a source to a destination via one or more
networks.

Layer 4: Transport layer
It provides transparent transfer of data between end users.

Layer 5: Session layer
It controls the sessions between computers. It connects, manages and terminates
the connections between the local and remote application.

Layer 6: Presentation
layer
It transforms data to provide a standard interface for the
Application layer.

Layer 7: Application layer
It provides a means for the user to access information on the network through
an application.

Define File
Transfer Protocol.

File Transfer Protocol (FTP), a
standard Internet protocol, is the simplest way to exchange files between
computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which
transfers displayable Web pages and related files, and the Simple Mail Transfer
Protocol (SMTP), which transfers e-mail, FTP is an application protocol that
uses the Internet’s TCP/IP protocols. FTP is commonly used to transfer Web page
files from their creator to the computer that acts as their server for everyone
on the Internet. It’s also commonly used to download programs and other files
to your computer from other servers.

What is FTP
(File Transfer Protocol)?

FTP is File Transfer Protocol. It
used to exchange files on the internet. To enable the data transfer FTP uses
TCP/IP, FTP is most commonly used to upload and download files from the
internet. FTP can be invoked from the command prompt or some graphical user
interface. FTP also allows to update (delete, rename, move, and copy) files at
a server. It uses a reserved port no 21

Define the
term Protocol.

Protocol is a standard way of
communicating across a network. A protocol is the “language” of the
network. It is a method by which two dissimilar systems can communicate. TCP is
a protocol which runs over a network.

What’s the
difference Between an Intranet and the Internet?

There’s one major distinction
between an intranet and the Internet: The Internet is an open, public space,
while an intranet is designed to be a private space. An intranet may be
accessible from the Internet, but as a rule it’s protected by a password and
accessible only to employees or other authorized users.

From within a company, an intranet
server may respond much more quickly than a typical Web site. This is because
the public Internet is at the mercy of traffic spikes, server breakdowns and
other problems that may slow the network. Within a company, however, users have
much more bandwidth and network hardware may be more reliable. This makes it
easier to serve high-bandwidth content, such as audio and video, over an
intranet.

What is LAN?

LAN is a computer network that
spans a relatively small area. Most LANs are confined to a single building or
group of buildings. However, one LAN can be connected to other LANs over any
distance via telephone lines and radio waves. A system of LANs connected in
this way is called a wide-area network (WAN). Most LANs connect workstations
and personal computers. Each node (individual computer) in a LAN has its own
CPU with which it executes programs, but it also is able to access data and
devices anywhere on the LAN. This means that many users can share expensive
devices, such as laser printers, as well as data. Users can also use the LAN to
communicate with each other, by sending e-mail or engaging in chat
sessions.

Explain the concepts and capabilities of IP Datagram.

Data transmitted over an
internet using IP is carried in messages called IP datagrams.
Like all network protocol messages, IP uses a specific format for its
datagrams.

The IPv4 consists of the
following fields:

Version: the version of IP used
to generate the datagram. For IPv4, this is of course the number 4
Internet Header Length:
Specifies the length of the IP header, in 32-bit words.
Type of service: information to
provide quality of service features
Total Length
Identification: it can be used
if the datagram must be fragmented by a router during delivery and then
for reassembling.
Flags: (Don’t Fragment, More
Fragment)
Fragment Offset: When
fragmentation of a message occurs, this field specifies the offset, or
position.
Time to Live: specifies how
long the datagram is allowed to “live”
Protocol: ICMP, TCP, UDP, etc
Header Checksum: to provide
basic protection against corruption in transmission.
Source Address
Destination Address
Options
Padding: if number of bits used
for options is not a multiple of 32, then paddin is added
Data

What is Data
Fragmentaion? Explain how Data Fragmentaion works

Fragmentation occurs when storage
space is used inefficiently due to which storage capacity and performance is
reduced.

Data fragmentation occurs when a
large object is inserted into storage that has already suffered external
fragmentation due to which the data object is broken up into many pieces that
are not close together.

When free storage becomes divided
into many small pieces over time, its called External fragmentation.

What is
VLSM, Variable length subnet masking?

VLSM is a means of allocating IP
addressing resources to subnets according to their individual need rather than
some general network-wide rule.

What is Superneting? Explain the concept of custom Subneting.

Supernetting or
Classless Inter-Domain Routing (CIDR)

It is a way to aggregate
multiple Internet addresses of the same class.
The adjacent network address
(eg:192.168.2.0/24 and an address 192.168.3.0/24) can be merged (into
192.168.2.0/23) using supernetting.
Supernetting is the basis for
most routing protocols currently used on the Internet.
It is mostly used to combine
Class C network addresses.

Describe the concept of Subneting.

Subneting is a process
of breaking the network into smaller units. These units care called as subnets.
Here a subnet could be several machines in a single LAN. Networks using IP can
create sub networks of logical addresses. With every IP address there some of
the bits in the machine can be used to identify a specific subnet. The IP
address then contains three parts: the network number, the subnet number, and
the machine number.

What is custom Subneting?

Subnets that can be
customized; i.e. modifying the dividing point between subnet ID and host ID to
suit the needs of our network. The subnet mask that we use when creating a
customized subnet is, called a custom subnet mask. This custom subnet mask is
used to find the customization..

What is
Subneting? Explain the advantages of using Subneting.

Subneting is dividing a network
into several subnets.
This is usually done for the following purposes:

Reducing
network traffic by decreasing the number of broadcasts
Exceeding
the limitations in a local area network
Enabling
people to connect to the network remotely without opening the entire
network

Explain the
advantages of using Subneting.

Advantages of using Subneting:-

Easier
network management and trouble shooting
Routing
table’s size is reduced which means faster network transfers
Solves
network congestion problems:- Since the complete network is divided into
smaller networks
Network
addresses can be decentralized e.g. the administrator of the network can
monitor the subnet.

Explain the
classes of IP addresses. Why do we need them?

Class A:
Range: from 0.0.0.0 to 127.255.255.255.
Leftmost bit: 0.
First 8 bits: netid.
Remaining 24 bits: hostid.

Class B:
Range: from 128.0.0.0 to 191.255.255.255.
Leftmost 2 bits: 10
First 16 bits: netid
Last 16 bits: the hostid

Class C:
Range: from 192.0.0.0 to 223.255.255.255.
Class C networks use the first 24 bits to determine the netid.
Leftmost 3 bits: 110
The next 21 bits define network.
8 bits define the hostid.

Class D:
First 4 bits: 1110
The remaining 28 bits define multicast addresses.
No netid or hostid in a class D address.
Addresses is used for multicasting.

Class E:
First 4 bits: 1111
Addresses reserved for special use on the Internet.
There is no netid or hostid in a class E address.

What is IP
Multicasting?

It is an IP address that
identifies a particular group of hosts in network.
This group of hosts is called a multicast group.

Explain the
concept and capabilities of Unicast IP Addresses

It is an IP address that uniquely
identifies a host in a network.
The datagram with a unicast IP address is received and processed by only a
single host.

Explain different layers in the OSI model.

Application Layer:

Closest to the end user
Interact directly with the
software application.

Presentation Layer:

Translates application to
network format, and vice versa
Works to transform data into
the form that the application layer can accept
Formats and encrypts data to be
sent across a network

Session Layer

Controls the connections
between computers
Establishes, manages and
terminates the connections between the local and remote application.
Provides full-duplex,
half-duplex, or simplex operation
Establishes checkpointing,
adjournment, termination, and restart procedures

Transport Layer:

Provides transparent transfer
of data between end users
Providing reliable data
transfer services to the upper layers
Controls the reliability of a
given link through flow control, segmentation / desegmentation, and error
control.

Network Layer

Provides the functional and
procedural means of transferring variable length data sequences from a
source to a destination via one or more networks
Performs networkrouting
functions
Performs fragmentation and
reassembly, and report delivery errors.

Data Link Layer

Provides the functional and
procedural means to transfer data between network entities
Detects and corrects errors
that occur in the Physical Layer.

Physical Layer:

Defines the electrical and
physical specifications for devices.

What is Router? Explain components of Routers.

The way switches connect
multiple computers, a router connects multiple networks. Routers comprise of
data consisting of large tables of networks and addresses. Routers use
algorithms to determine the shortest route to an address in a network.

What are the basic components of routers?

Answer

Components of Router

Internal components:

ROM:- Used to store the routers
bootstrap details, operating system software.
Flash memory: – holds the
operating systems images. The content is retained when the router is
restarted.
RAM: – Used to store the
Routing tables, configuration files, caching and buffering details.
Content is lost when lost router is switched off or restarted.
NVRAM:- Stores the routers
startup config files. Data is non volatile.
Network interfaces to connect
router to network.

External components:

Virtual terminals: For
accessing routers
Network management stations.

What are
switches? Explain the concepts of Layer-3 switches.

It is a device that connects
multiple network segments.
A switch analyzes the MAC address and then determines where to send the data.
So a file addressed to a computer reaches only that computer through the use of
a switch.
The term ‘switch’ commonly refers to a Network bridge that processes and routes
data at the Data link layer (layer 2) of the OSI model.

Switches that additionally
process data at the Network Layer are often referred to as Layer 3 switches or
Multilayer switches.

What is
‘Gateway Of Last Resort’?

A Gateway of Last Resort or
Default gateway is a route used by the router when no other known route exists
to transmit the IP packet. Known routes are present in the routing table.
Hence, any route not known by the routing table is forwarded to the default
route. Each router which receives this packet will treat the packet the same
way, if the route is known, packet will be forwarded to the known route.

Explain
Circuit Level Gateway.

A circuit level gateway is used
to find if a session in TCP handshaking is legitimate or not. It can be
considered as a layer between application layer and transport layer. They
protect the information of the private network they protect. Circuit level
gateways do not filter packets.

What is an
application gateway?

An application gateway is an
application program that runs on a firewall between two networks. An
application gateway is used for establishing connection between client program
and destination service. The client negotiates with the gateway to communicate
with the service of destination. Here, gateway can be called as a proxy. Hence,
two connections are made. One between client and proxy; other, between proxy
and destination service. Connections take place behind the firewall

Explain IP
datagram, Fragmentation and MTU.

IP datagram can be used to
describe a portion of IP data. Each IP datagram has set of fields arranged in
an order. The order is specific which helps to decode and read the stream
easily. IP datagram has fields like Version, header length, Type of service,
Total length, checksum, flag, protocol, Time to live, Identification, source
and destination ip address, padding, options and payload.

MTU:- Maximum Transmission Unit
is the size of the largest packet that a communication protocol can pass. The
size can be fixed by some standard or decided at the time of connection

Fragmentation is a process of
breaking the IP packets into smaller pieces. Fragmentation is needed when the
datagram is larger than the MTU. Each fragment becomes a datagram in itself and
transmitted independently from source. When received by destination they are
reassembled.

What is IP
Spoofing and how can it be prevented?

IP spoofing is a mechanism used
by attackers to gain unauthorized access to a system. Here, the intruder sends
messages to a computer with an IP address indicating that the message is coming
from a trusted host. This is done by forging the header so it contains a
different address and make it appear that the packet was sent by a different
machine.

Prevention:-
Packet filtering: – to allow packets with recognized formats to enter the
network
Using special routers and firewalls.
Encrypting the session

What is PPP
protocol? Explain PPP packet format.

Point to Point protocol helps
communication between 2 computers over a serial cable, phone line or other
fiber optic lines. E.g. Connection between an Internet Service Provider and a
host. PPP also provides authentication. PPP operates by sending Request packets
and waiting for Acknowledge packets that accept, reject or try to change the
request. The protocol is also used to negotiate on network address or
compression options between the nodes.

Packet format:-

Flag field: 1 byte: – Indicates
frames beginning or end
Address field: 1 byte: – Used for broadcast address (destination address)
Control field: 1 byte: – Used as a control byte
Protocol field: – 1 or 2 bytes: – Setting of protocol in information field (of
datagram)
Information: – 0 or more bytes: – Datagram (whether it contains data or control
information)
Padding: – 0 or more bytes: – optional padding
FCS: – 2 or more bytes: – error check sum

Explain how
NAT works.

Network Address Translation
translates and IP address used in a network to another IP address known within
another network. A NAT table is maintained for global to local and local to
mapping of IP’s. NAT can be statically defined or dynamically translate from a
pool of addresses. The NAT router is responsible for translating traffic coming
and leaving the network. NAT prevents malicious activity initiated by outside
hosts from reaching local hosts by being dependent on a machine on the local
network to initiate any connection to hosts on the other side of the router.

What are the
differences between a domain and a workgroup?

In a domain, one or more computer
can be a server to manage the network. On the other hand in a workgroup all
computers are peers having no control on each other. In a domain, user doesn’t
need an account to logon on a specific computer if an account is available on
the domain. In a work group user needs to have an account for every computer.
In a domain, Computers can be on different local networks. In a work group all
computers needs to be a part of the same local network.

Explain the
concept of DHCP.

Dynamic Host Configuration
Protocol is used assigning IP addresses to computers in a network. The IP
addresses are assigned dynamically. Certainly, using DHCP, the computer will
have a different IP address every time it is connected to the network. In some
cases the IP address may change even when the computer is in network. This
means that DHCP leases out the IP address to the computer for sometime. Clear
advantage of DHCP is that the software can be used to manage IP address rather
than the administrator.

Explain
RSVP. How does it work?

Resource Reservation protocol is
used to reserve resources across a network. It is used for requesting a
specific Quality of Service (QoS) from the network. This is done by carrying
the request (that needs a reservation of the resource) of the host throughout
the network. It visits each node in the network. RSVP used two local modules
for reservation of resources. Admission control module confirms if there are
sufficient available resources while policy module checks for the permission of
making a reservation. RSVP offers scalability. On a successful completion of
both checks RSVP uses the packet classifier and packet scheduler for the desired
Qos requested.

What are
Ping and Tracert?

Ping and tracert are the commands
used to send information to some remote computers to receive some information.
Information is sent and received by packets. Ping I particularly used to check
if the system is in network or not. It also gives packet lost information. In
windows ping command is written as ping ip_address Tracert is called as trace
route. It is used to track or trace the path the packet takes from the computer
where the command is given until the destination. In windows ping command is
written as tracert ip_address

What is the
use of IGMP protocol?

Internet Group Management
Protocol: – It allows internet hosts to participate in multicasting. The IGMP
messages are used to learn which hosts is part of which multicast groups. The
mechanism also allow a host to inform its local router, that it wants to
receive messages.

Explain the
use of Internet Control Message Protocol (ICMP).

Internet Control Message Protocol
is one of the important protocols in the Internet Protocol suite. It is mainly
used in operating system of networked computers, for the purpose of sending
error messages, for example, a requested service is unavailable or the host
could not be reached. It is not directed by the network applications. ICMPs are
utilized by routers, hosts for communicating the updates or error information
to other routers.

What is the
TTL (Time to Live)? Why is it required?

TTL is a value in data packet of
Internet Protocol. It communicates to the network router whether or not the
packet should be in the network for too long or discarded. Usually, data
packets might not be transmitted to their intended destination within a
stipulated period of time. The TTL value is set by a system default value which
is an 8-bit binary digit field in the header of the packet. The purpose of TTL
is, it would specify certain time limit in seconds, for transmitting the packet
header. When the time is exhausted, the packet would be discarded. Each router
receives the subtracts count, when the packet is discarded, and when it becomes
zero, the router detects the discarded packets and sends a message, Internet
Control Message Protocol message back to the originating host.

What is the
Domain Name System (DNS)? What are the advantages of it?

A hierarchical naming system for
computer systems, services or for that matter any resource participating in the
internet. Various information with domain names is assigned to each of the
participants. DNS translates the names of domain into meaningful to humans into
binary identifiers that are associated with the equipment of network to locate
and address these devices.

Advantages:

More Reliable: Delivers messages to the users with zero
downtime.

Faster: DNS are connected well at intersections of internet.
Any cast technology enables requests are answered to the next closest node in
the case of maintenance or downtime.

Smarter: Automatic corrections of typos.

Explain TCP
Windowing concept.

TCP Windowing is a concept that
is used for avoiding congestion in the network traffic. Unacknowledged amount
of data that is sent by the sender before the data gets acknowledgment back
from the receiver that it has received it is controlled.

What is the
User Datagram Protocol (UDP)?

User datagram protocol allows
computer applications to send messages as datagram packets from source to
destination on an Internet Protocol, with out using prior communications for
setting up special transmission paths. An unreliable service is provided by UDP
which makes the datagram packets may arrive irrespective of order. UDP is a
better solution for time-sensitive applications due to the reason ‘dropping
packets is preferable to use delayed packets’. Its stateless nature makes the
server to answer smaller queries to huge number of clients.

Define
Subnetting.

A subnet describes a set of
networked computers which have common IP address routing prefix.

Breaking the networking into
smaller and more efficient subnets is known as subnets. Subnetting prevents
Ethernet packet collision which has excessive rates in a large network. Routers
are used to manage the traffic and constitute borders among subnets.

What is
Network Mask?

A network mask is used for
determination of what subnet an IP address belongs to. An IP address has
network address and the host address. The first two numbers represents the
network address and the second two numbers represents the host of the
network.

Define
Broadcast, Unicast and Multicast.

Unicast: A term used in communication to describe a
piece of information to send from one point to another. There are only sender
and receiver. All LANs support unicast transfer mode and most applications that
employ TCP transport protocol uses unicast messaging.

Broadcast: A term used for describing communication that
is sent a piece of information from one point to all other points. There is one
sender and multiple receivers. All LANs support broadcast transmission.

Multicast: A term described in communicating a piece of
information sent from one or more points to a set of other points. The senders
and receivers are one or more.

Explain the
classes of IP address

IP addresses are organized into
classes. For convenience of humans, IP addresses are expressed in the decimal
format. Every number in each class is represented as binary to computers.

The four numbers in an IP address
are known as ‘octets’. Each of them has eight bit positions. The octets are
divided into two sections: Net and Host. The first octet represents Net for
identifying the network and the Host contains the last octet. There are five IP
classes.

Class A: The class A is used for very large networks.
There are 1 to 126 are part of this class. That means there are 126 Class A
networks. Class A networks accounts for half of the total available IP
addresses.

Class B: It is used for medium size networks. The IP
address with a first octet from 128 to 191 is part of this class. Class B
networks have a first bit value of 1 and a second bit value of 0 in the first
octet.

Class C: Class C is used for small to middle size networks.
IP address with a first octet starts from 192-223. Class C networks have a
first bit value of 1, second bit value of 1 and a third bit value of 0 in the
first octet.

Class D: It has first, second and third bit value as 1
and the fourth bit as 0. The other 28 bits are used for identifying the group
of computers which is intended for multicast messages.

Class E: Class E is used for identification purpose.
The four bits value is 1. The other 28 bits are used for identifying the group
of computers which is intended for multicast messages.

Explain the
services provided by IP (Internet Protocol) – Addressing, Fragmentation, Packet
timeouts and options

1. Addressing: For the purpose of delivering datagram
packets, IP needs to know about the address of the destination. By including
the host addressing, this task is carried out by IP. As IP operates in an
internet, its systems are designed to accept the addressing of devices which
are unique.

2. Fragmenting: The datagram packets are sent to the data
link layer for the purpose of transmission on the network. The physical network
frame size that uses IP may be different. To resolve this, IP fragments the
datagram into certain pieces. So that, each piece can be carried on the
network. The receiving systems use these pieces and reassemble the whole IP
datagram again.

3. Packet timeouts: A timeout packet is the time for waiting next
instruction from the command station. If the command is not sent by the
station, it shuts down.

The Open System Interconnection Model

The Open System
Interconnection (OSI) model specifies how dissimilar computing devices such as
Network Interface Cards (NICs), bridges and routers exchange data over a
network by offering a networking framework for implementing protocols in seven
layers. Beginning at the application layer, control is passed from one layer to
the next. The following describes the seven layers as defined by the OSI model,
shown in the order they occur whenever a user transmits information.

Layer 7: Application

This
layer supports the application and end-user processes. Within this layer, user
privacy is considered and communication partners, service and constraints are
all identified. File transfers, email, Telnet and FTP applications are all
provided within this layer.

Layer 6: Presentation
(Syntax)

Within
this layer, information is translated back and forth between application and
network formats. This translation transforms the information into data
the application layer and network recognize regardless of encryption and
formatting.

Layer 5: Session

Within
this layer, connections between applications are made, managed and terminated
as needed to allow for data exchanges between applications at each end of a
dialogue.

Layer 4: Transport

Complete
data transfer is ensured as information is transferred transparently between
systems in this layer. The transport layer also assures appropriate flow
control and end-to-end error recovery.

Layer 3: Network

Using
switching and routing technologies, this layer is responsible for creating
virtual circuits to transmit information from node to node. Other functions
include routing, forwarding, addressing, internetworking, error and congestion
control, and packet sequencing.

Layer 2: Data Link

Information
in data packets are encoded and decoded into bits within this layer. Errors
from the physical layer flow control and frame synchronization are corrected
here utilizing transmission protocol knowledge and management. This layer
consists of two sub layers: the Media Access Control (MAC) layer, which
controls the way networked computers gain access to data and transmit it, and
the Logical Link Control (LLC) layer, which controls frame synchronization,
flow control and error checking.

Layer 1: Physical

This
layer enables hardware to send and receive data over a carrier such as cabling,
a card or other physical means. It conveys the bitstream through the network at
the electrical and mechanical level. Fast Ethernet, RS232, and ATM are all
protocols with physical layer components.

This order is then reversed as
information is received, so that the physical layer is the first and
application layer is the final layer that information passes through.

General
Topology Configurations

10BASE-T Ethernet and Fast
Ethernet use a star topology where access is controlled by a central computer.
Generally a computer is located at one end of the segment, and the other end is
terminated in central location with a hub or a switch. Because UTP is often run
in conjunction with telephone cabling, this central location can be a telephone
closet or other area where it is convenient to connect the UTP segment to a
backbone. The primary advantage of this type of network is reliability, for if
one of these ‘point-to-point’ segments has a break; it will only affect the two
nodes on that link. Other computer users on the network continue to operate as
if that segment were non-existent.

Collisions

Ethernet is a shared medium, so
there are rules for sending packets of data to avoid conflicts and to protect
data integrity. Nodes determine when the network is available for sending
packets. It is possible that two or more nodes at different locations will
attempt to send data at the same time. When this happens, a packet collision
occurs.

Minimizing collisions is a
crucial element in the design and operation of networks. Increased collisions
are often the result of too many users on the network. This leads to
competition for network bandwidth and can slow the performance of the network
from the user’s point of view. Segmenting the network is one way of reducing an
overcrowded network, i.e., by dividing it into different pieces logically
joined together with a bridge or switch.

CSMA/CD

In order to manage collisions
Ethernet uses a protocol called Carrier Sense Multiple Access/Collision
Detection (CSMA/CD). CSMA/CD is a type of contention protocol that defines how
to respond when a collision is detected, or when two devices attempt to
transmit packages simultaneously. Ethernet allows each device to send messages
at any time without having to wait for network permission; thus, there is a
high possibility that devices may try to send messages at the same time.

After detecting a collision,
each device that was transmitting a packet delays a random amount of time
before re-transmitting the packet. If another collision occurs, the device
waits twice as long before trying to re-transmit.

Ethernet Products

The standards and technology
just discussed will help define the specific products that network managers use
to build Ethernet networks. The following presents the key products needed to
build an Ethernet LAN.

Transceivers

Transceivers are also referred
to as Medium Access Units (MAUs). They are used to connect nodes to the various
Ethernet media. Most computers and network interface cards contain a built-in
10BASE-T or 10BASE2 transceiver which allows them to be connected directly to
Ethernet without the need for an external transceiver.

Many Ethernet devices provide
an attachment unit interface (AUI) connector to allow the user to connect to any
type of medium via an external transceiver. The AUI connector consists of a
15-pin D-shell type connector, female on the computer side, male on the
transceiver side.

For Fast Ethernet networks, a
new interface called the MII (Media Independent Interface) was developed to
offer a flexible way to support 100 Mbps connections. The MII is a popular way
to connect 100BASE-FX links to copper-based Fast Ethernet devices.

Network Interface Cards

Network Interface Cards,
commonly referred to as NICs, are used to connect a PC to a network. The NIC
provides a physical connection between the networking cable and the computer’s
internal bus. Different computers have different bus architectures. PCI bus
slots are most commonly found on 486/Pentium PCs and ISA expansion slots are
commonly found on 386 and older PCs. NICs come in three basic varieties: 8-bit,
16-bit, and 32-bit. The larger the number of bits that can be transferred to
the NIC, the faster the NIC can transfer data to the network cable. Most NICs
are designed for a particular type of network, protocol, and medium, though
some can serve multiple networks.

Many NIC adapters comply with
plug-and-play specifications. On these systems, NICs are automatically
configured without user intervention, while on non-plug-and-play systems,
configuration is done manually through a set-up program and/or DIP switches.

Cards are available to support
almost all networking standards. Fast Ethernet NICs are often 10/100 capable,
and will automatically set to the appropriate speed. Gigabit Ethernet NICs are
10/100/1000 capable with auto negotiation depending on the user’s Ethernet
speed. Full duplex networking is another option where a dedicated connection to
a switch allows a NIC to operate at twice the speed.

Hubs/Repeaters

Hubs/repeaters are used to
connect together two or more Ethernet segments of any type of medium. In larger
designs, signal quality begins to deteriorate as segments exceed their maximum
length. Hubs provide the signal amplification required to allow a segment to be
extended a greater distance. A hub repeats any incoming signal to all ports.

Ethernet hubs are necessary in
star topologies such as 10BASE-T. A multi-port twisted pair hub allows several
point-to-point segments to be joined into one network. One end of the
point-to-point link is attached to the hub and the other is attached to the
computer. If the hub is attached to a backbone, then all computers at the end
of the twisted pair segments can communicate with all the hosts on the
backbone. The number and type of hubs in any one-collision domain is limited by
the Ethernet rules. These repeater rules are discussed in more detail later.

A very important fact to note
about hubs is that they only allow users to share Ethernet. A network of
hubs/repeaters is termed a “shared Ethernet,” meaning that all
members of the network are contending for transmission of data onto a single network
(collision domain). A hub/repeater propagates all electrical signals including
the invalid ones. Therefore, if a collision or electrical interference occurs
on one segment, repeaters make it appear on all others as well. This means that
individual members of a shared network will only get a percentage of the
available network bandwidth.

Types of Networks

In describing the basics of
networking technology, it will be helpful to explain the different types of
networks in use.

Local Area Networks (LANs)

A network is any collection of
independent computers that exchange information with each other over a shared
communication medium. Local Area Networks or LANs are usually confined to a
limited geographic area, such as a single building or a college campus. LANs
can be small, linking as few as three computers, but can often link hundreds of
computers used by thousands of people. The development of standard networking
protocols and media has resulted in worldwide proliferation of LANs throughout
business and educational organizations.

Wide Area Networks (WANs)

Often elements of a network are
widely separated physically. Wide area networking combines multiple LANs that
are geographically separate. This is accomplished by connecting the several
LANs with dedicated leased lines such as a T1 or a T3, by dial-up phone lines
(both synchronous and asynchronous), by satellite links and by data packet
carrier services. WANs can be as simple as a modem and a remote access server
for employees to dial into, or it can be as complex as hundreds of branch
offices globally linked. Special routing protocols and filters minimize the
expense of sending data over vast distances.

Wireless Local Area Networks (WLANs)

Wireless LANs, or WLANs, use
radio frequency (RF) technology to transmit and receive data over the air. This
minimizes the need for wired connections. WLANs give users mobility as they
allow connection to a local area network without having to be physically
connected by a cable. This freedom means users can access shared resources without
looking for a place to plug in cables, provided that their terminals are mobile
and within the designated network coverage area. With mobility, WLANs give
flexibility and increased productivity, appealing to both entrepreneurs and to
home users. WLANs may also enable network administrators to connect devices
that may be physically difficult to reach with a cable.

The Institute for Electrical
and Electronic Engineers (IEEE) developed the 802.11 specification for wireless
LAN technology. 802.11 specifies over-the-air interface between a wireless
client and a base station, or between two wireless clients. WLAN 802.11
standards also have security protocols that were developed to provide the same
level of security as that of a wired LAN.
The first of these protocols is Wired Equivalent Privacy (WEP). WEP provides
security by encrypting data sent over radio waves from end point to end point.

The second WLAN security
protocol is Wi-Fi Protected Access (WPA). WPA was developed as an upgrade to
the security features of WEP. It works with existing products that are
WEP-enabled but provides two key improvements: improved data encryption through
the temporal key integrity protocol (TKIP) which scrambles the keys using a
hashing algorithm. It has means for integrity-checking to ensure that keys have
not been tampered with. WPA also provides user authentication with the
extensible authentication protocol (EAP).

Problem Description

I need a list of common
Windows commands to help me troubleshoot Websense in my network.

Resolution

The Windows troubleshooting
commands discussed in this document fall into three categories:

·
Determine which groups a user belongs

·
Helpful commands entered from the Start > Run dialog box

·
Comman-line tools for troubleshooting network connectivity

Determine which groups a user belongs

To
generate a list of groups that a user belongs, open a command prompt and enter
the following commands:

   net user  /domain

Replace with an actual user name. For
example:

   net user jdoe /domain

Helpful commands entered from the Start >
Run dialog box

Select Start > Run to execute any of the following commands. mstsc	Opens the Remote Desktop (RDP) tool
winmsd	Opens the System Information dialog box
inetcpl.cpil	Opens the Internet Explorer Properties dialog box
odbccp32.cpl	Opens the ODBC Data Source Administrator
mmc	Opens the Microsoft Management Console (MMC)
services.msc	Opens the Windows Services dialog box
eventvwr.msc	Opens the Windows Event Viewer
dsa.msc	Opens the Active Directory User and Computers management console
dssite.msc	Opens the Active Directory Sites and Services management console
adminpak.msi	Launches the Administration Tools Pack installer
dxdiag	Opens the DirectX Diagnostic Tool
\\\C$	Opens a UNC to the C: share
cmd	Opens the Windows Command Prompt using the 32-bit cmd shell

Command-line
tools for troubleshooting network connectivity

This
list contains some common commands for troubleshooting network connectivity.
Select Start > Run and then type cmd to access the appropriate command prompt. Activating a command
window viaStart > Programs > Accessories does not allow all of the following tools to run correctly.

User-added image

arp -a	Shows gateway MAC address.
gpresult	Starts the Operating System Group Policy Result tool
ipconfig /all	Displays the full TCP/IP configuration for all adapters
ipconfig /flushdns	Flushes the DNS resolver cache. Helpful when troubleshooting DNS name resolution problems
nbtstat -a	Obtains info from WINS or LMHOST (discovers who is logged on)
nbtstst -A	Gets info from WINS or LMHOST (discovers who is logged on)
nbtstat -R	Purges and reloads the remote cache name table
nbtstat -n	Lists local NetBIOS names.
nbtstat -r	Useful for detecting errors when browsing WINS or NetBIOS
netstat -ab	The b switch links each used port with its application
netstat -an	Shows open ports
netstat -an 1 \| find “15868”	Locates only lines with the number 15868 and redisplays every one second
netstat -an \| find “LISTENING”	Shows open ports with LISTENING status
net use	Retrieves a list of network connections
net use file://1.2.3.4/	Sees if the machine can poll IP 1.2.3.4
net user	Shows user account for the computer
net user /domain	Displays user accounts for the domain
net user /domain	Shows account details for specific user
net group /domain	Shows group accounts for the domain
net view	Displays domains in the network
net view /domain	Specifies computers available in a specific domain
net view /domain: \| more	Shows user accounts from specific domain
net view /cache	Shows workstation names
nslookup	Looks up IP/hostnames and displays information helpful in diagnosing DNS issues
ping -a	Resolves IP to Hostname
ping -t	Pings host until stopped
set U	Shows which user is logged on
set L	Shows the logon server
telnet	Confirms whether the port is open

net use %LOGONSERVER%

·
Use this command to hit the Domain Controller resulting in
DC Agent picking up the user name you logged onto the server with. An
example of the command follows:

·
net use \\<Domain Controller IP or Hostname>

Notes & Warnings

NOTE

Some commands may output more data then the
default command window can show. To view the complete data, use the pipe
command ( > or | ) to direct the output to a file. For example, type net user \domain > GroupOutPut.txt to create a text file called GroupOutPut.txt that contains the output data.

ipconfig – Quickly Find Your IP Address

You can find your IP address from the Control
Panel, but this takes quite a few clicks. The ipconfig command is a fast way of
determining your computer’s IP address and other information, such as the
address of its default gateway — useful if you want to know the IP address of
your router’s web interface.

To use the command, just type ipconfig into
a Command Prompt window. You’ll see a list of all the network connections your
computer is using. Look under Wireless LAN adapter if you’re connected to Wi-Fi
or Ethernet adapter Local Area Connection if you’re connected to a wired
network.

ipconfig-command[4]

ipconfig /flushdns – Flush Your DNS Resolver Cache

If you change your DNS server, the effects won’t necessarily take place
immediately. Windows uses a cache that remembers DNS responses it’s received, saving
time when you access the same addresses again in the future.

To ensure Windows is getting addresses from
the new DNS servers instead of using old, cached entries, run the ipconfig
/flushdns command after changing your DNS server.

flush-dns-resolver-cache

ping, tracert – Troubleshoot Network Connection Issues

If you’re experiencing issues connecting to a
website or other network connection issues, Windows and other operating systems
have some standard tools you can use to identify problems.

First, there’s the ping command. Type ping
google.com and Windows will send packets to Google.com. Google will
respond and let you know it’s received them. You’ll be able to see if any
packets didn’t make it to Google.com — perhaps you’re experiencing packet loss
— and how long it took you to hear back — perhaps the network is saturated and
packets are taking a while to reach their destinations.

ping-command-on-windows

There’s also the tracert command, which traces
the route it takes for a packet to reach a destination. For example, run tracert
google.com and you’ll see the path your packet takes to reach Google.
If you’re having issues connecting to a website, tracert can show you where the
problem is occurring.

tracert-command-on-windows

For more information about using these
commands, read our introduction to troubleshooting Internet
connection problems.

shutdown – Create Shutdown Shortcuts on Windows 8

The shutdown command is particularly useful on
Windows 8. You can use it to create your own shortcuts and place them on
your Start screen or desktop,
allowing you to more easily shut down Windows without digging through the charms
bar or logging out first.

This command can also be used to restart your
computer. On Windows 8, you can even use a special switch to restart your
computer into the advanced startup options menu.

·
Shut Down: shutdown
/s /t 0

·
Restart: shutdown
/r /t 0

·
Restart Into Startup
Options: shutdown /r /o

create-shut-down-shortcut-on-windows-8

recimg – Create Custom Recovery Images

The Refresh Your PC feature on Windows 8 allows you to restore your computer’s
system state to its original state — either from a clean Windows install or as
the computer came from its manufacturer. You can create your own custom
recovery images, but this feature is hidden — you have to do it with the recimg command
from a command line. This allows you to removemanufacturer-installed bloatware or add your favorite desktop programs to
your recovery image.

For more information about using recimg, read
our overview of everything you need to know about creating and
using custom recovery images on Windows 8.

wbadmin start backup – Create System Recovery Images

Windows 8.1 removes the Windows 7 backup interface, which allowed you to create system backup
images. These system images contain a complete snapshot of every single file on
the system, so they’re different from Windows 8’s recovery images.

While the graphical interface has been
removed, system administrators and geeks can still create system image backups
by running the wbadmin start backup cmdlet in a
PowerShell window. Unlike all the other
commands here, this command-line tool must be run from within PowerShell, not
the Command Prompt.

sfc /scannow – Scan System Files for Problems

Windows includes a system file checker tool
that scans its system files and looks for problems. If system files are missing
or corrupted, the system file checker will repair them. This may fix problems
with some Windows systems.

To use this tool, open a Command Prompt window
as Administrator and run the sfc /scannowcommand.

sfc-scannow

telnet – Connect to Telnet Servers

The telnet client isn’t installed by default.
You’ll have to install it from the Control Panel. Once installed, you can use
the telnet command to connect to telnet servers without
installing any third-party software.

You should avoid using telnet if you can help
it, but if you’re connected directly to a device and it requires that you use telnet
to set something up — well, that’s what you have to do.

install-windows-telnet-client

cipher – Permanently Delete and Overwrite a Directory

The cipher command is mostly used for managing
encryption, but it also has an option that will write garbage data to a drive,
clearing its free space and ensuring no deleted file can be recovered. Deleted files normally stick around on disk unless you’re using a solid state drive.
The cipher command effectively allows you to “wipe” a drive without installing
any third-party tools.

To use the command, specify the drive you want
to wipe like so:

ciper /w:C:\

cipher wipe drive

netstat -an – List Network Connections and Ports

The netstat command is particularly useful,
displaying all sorts of network statistics when used with its various options.
One of the most interesting variants of netstat is netstat -an,
which will display a list of all open network connections on their computer,
along with the port they’re using and the foreign IP address they’re connected
to.

netstat-show-connections k
Connecvity

§ Troubleshooting
Network Connectivity Issues

§ Required
Ports for Steam

§ Known
Issues with Internet Service Providers (ISPs)

Important:

Before
proceeding with troubleshooting, please check the Steam Server Status page to ensure the issue which you are
encountering is not related
to system-wide downtime. (If you encounter any timeout errors when attempting
to access Steam sites, it is very likely that there is a system-wide issue and
Steam will not be accessible until the issue is resolved)

sues

Please
follow the steps below to diagnose network connectivity issues within Steam:

1.
Test Your Router trying
anything else:

Try bypassing your router by
connecting your computer directly to your modem.

If the issue disappears after
bypassing your router, please refer to the Using a Router with Steam topic for instructions on configuring your
router.

Note:
running your router in DMZ mode is not supported by Steam and may result in
connection issues.

Additionally, wireless
connections are not recommended for online gaming. To ensure reliability,
make sure you are using a wired connection to the internet while playing
online.

2.
Troubleshoot all Firewalls

See the Using a Firewall with Steam topic for instructions to properly
configure your firewall for Steam.

Note: If you are installing Steam for the first
time or Steam has recently been updated, a firewall may be preventing Steam
from connecting to the Steam Network – even if Steam worked correctly before
the update was applied.

3.
Disable Background Applications

Review the Programs
Which May Interfere With Steam and
reconfigure, disable or uninstall any programs which may be preventing Steam
and Valve games from connecting.

4.
Viruses, Trojans, Adware and
Spyware

Scan your computer for Spyware,
Adware, and Viruses Interfering with Steam.

5.
Power Cycle Your Network
Hardware

If the issue persists, unplug your
modem and router, wait a few seconds, then plug them back in. Sometimes, these
devices simply need to be refreshed.

6.
Try Launching Steam using TCP

Start Steam with the
“-tcp” launch option. Please see the Setting
Steam Launch Optionstopic for instructions.

Required Ports for Steam

All
required ports to run the Steam application are listed here.
It is possible that other games available on Steam will require further
ports to be available.

Note:

Many
university networks and proxies block required ports for Steam operation –
please consult your network administrator to ensure the required ports are open
if you are using a university network or a proxy. Ports required for Steam
can not be re-mapped to HTTP or reconfigured to a custom port range.

If you
notice that your Steam connection only has issues during certain hours of the
day (usually in the evenings between 5pm and 11pm), it is probable that your
ISP is blocking or “shaping” your connection. Please test your
connection at other hours of the day and contact your ISP directly if you
believe this is causing the connection issue.

There
are several ISPs which block ports required for the proper operation of Steam
and Steam games:

§ 012.net (Steam traffic blocked)

§ Bluewin (Firewall blocks Steam from provider side –
must be disabled through provider’s service portal)

§ Dutch
Telecom (Steam
traffic blocked)

§ ISPFree (Steam traffic blocked)

§ Micronet
Broadband (Steam
traffic blocked)

There
are connection issues with certain ISPs that can be avoided depending on what
type of cable/DSL modem and router you have.

Please
follow the guide for Client
dropped by ser

[the-post-grid id=”9538″ title=””]

desktop support, interview question and answer, network engineer, Network Security interview questions and answers

dixitra20

Questions for Network Engineer / Network Administrator (Security)

Collision Domain

Broadcast Domain

Difference between Static and Dynamic IP.

What is the difference between public and private IP?

What is Network Address Translation?

Define IP multicast.

What is subneting?

Define Address Resolution Protocol.

Explain Maximum Transfer Unit, MTU.

What is Routing Protocol?

Explain the structure and use of internet addresses.

Explain how names are translated (resolved) into IP address.

Describe the basics of internet routing.

Define broadcast domain.

Bridge vs switch

What is a Router?

Define gateway

What is firewall?

What are the types of firewalls?

What is Data encryption?

What is the Public Key Encryption?

Define Digital Signatures.

What is Ethernet technology?

What is CSMA and CD concept?

What is NetBIOS protocol?

What is IGMP protocol?

What is TCP / IP protocol?

What is HTTP (Hypertext Transfer Protocol)?

What is NNTP (Network News Transfer Protocol)?

What is POP3 (Post Office Protocol 3)?

What is SNMP (Simple Network Management Protocol)?

What is Routing Protocols?

What is Distance Vector Routing Protocols?

Explain Transmission Control Protocol, TCP

What is TCP protocol?

TCP vs. UDP.

Explain User Datagram Protocol, UDP.

What is UDP protocol?

TCP vs. UDP.

What is TCP windowing concept?

What is Trusted and Untrusted Networks?

What is Tunneling?

What are voluntary and compulsory tunnels?

Explain static and dynamic tunnels.

Explain the importance of increasing and decreasing subnet bits.

Why do we need a subnet mask?

What is RTP?

What is RTP Multiplexing?

Explain the use of RTP and RTCP protocols.

Describe the format of RTP and RTCP packets.

Describe how the multicast protocol works.

Describe how to control the scope of multicast transmissions.

What is a socket?

What are Sockets? How do Sockets Work?

Datagram vs. stream.

What is a stream socket?

What is SSL?

What is meant by Symmentric Multiprocessing (SMP)?

What are TP-Lite and TP-Heavy Monitors?

What is Distance Vector Routing Protocols?

What is POP3 (Post Office Protocol 3)?

What is NNTP (Network News Transfer Protocol)?

What is HTTP (Hypertext Transfer Protocol)?

What is IGMP protocol?

Define gateway

Explain how names are translated (resolved) into IP address.

Explain the structure and use of internet addresses.

Define IP multicast.

What is Network Address Translation?

What is the difference between public and private IP?

How would you define IP address?

MAC vs. IP Addressing

Define Telnet

Define DNS

What is Application layer?

Explain the core naming mechanism, Domain Name System (DNS).

Explain the functionality of PING.

What is multicasting?

Explain IP, TCP and UDP.

Difference
between Static and Dynamic IP.

What is the
difference between public and private IP?

What is
Network Address Translation?

Define IP
multicast.

What is
subneting?

Define
Address Resolution Protocol.

Explain
Maximum Transfer Unit, MTU.

What is
Routing Protocol?

Explain the
structure and use of internet addresses.

Explain how
names are translated (resolved) into IP address.

Describe the
basics of internet routing.

Define
broadcast domain.

Bridge vs
switch

What is a
Router?

Define
gateway

What is
firewall?

What are the
types of firewalls?

What is Data
encryption?

What is the
Public Key Encryption?

Define
Digital Signatures.

What is
Ethernet technology?

What is CSMA
and CD concept?

What is
NetBIOS protocol?

What is IGMP
protocol?

What is TCP
/ IP protocol?

What is HTTP
(Hypertext Transfer Protocol)?

What is NNTP
(Network News Transfer Protocol)?

What is POP3
(Post Office Protocol 3)?

What is SNMP
(Simple Network Management Protocol)?

What is Routing
Protocols?

What is
Distance Vector Routing Protocols?

Explain
Transmission Control Protocol, TCP

What is TCP
protocol?

Explain User
Datagram Protocol, UDP.

What is UDP
protocol?

What is TCP
windowing concept?

What is
Trusted and Untrusted Networks?

What is
Tunneling?

What are
voluntary and compulsory tunnels?

Explain
static and dynamic tunnels.

Explain the
importance of increasing and decreasing subnet bits.

Why do we
need a subnet mask?

What is
RTP?

What is RTP
Multiplexing?

Explain the
use of RTP and RTCP protocols.

Describe the
format of RTP and RTCP packets.

Describe how
the multicast protocol works.

Describe how
to control the scope of multicast transmissions.

What is a
socket?

What are
Sockets? How do Sockets Work?

Datagram vs.
stream.

What is a
stream socket?

What is
meant by Symmentric Multiprocessing (SMP)?

What are
TP-Lite and TP-Heavy Monitors?

What is
Distance Vector Routing Protocols?

What is POP3
(Post Office Protocol 3)?

What is NNTP
(Network News Transfer Protocol)?

What is HTTP
(Hypertext Transfer Protocol)?

What is IGMP
protocol?

Define
gateway

Explain how
names are translated (resolved) into IP address.

Explain the
structure and use of internet addresses.

Define IP
multicast.

What is
Network Address Translation?

What is the
difference between public and private IP?

How would
you define IP address?

MAC vs. IP
Addressing

Define
Telnet

What
is Application layer?

Explain the
core naming mechanism, Domain Name System (DNS).

Explain the
functionality of PING.

What is
multicasting?

Explain IP,
TCP and UDP.

What is a
network? What are the different kinds of network? Explain them

Explain the
7 Layers of OSI.

Define File
Transfer Protocol.

What is FTP
(File Transfer Protocol)?

Define the
term Protocol.

What’s the
difference Between an Intranet and the Internet?

What is Data
Fragmentaion? Explain how Data Fragmentaion works