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Key Observations
Symptom Analysis:
Random periods of packet loss, latency, and performance degradation.
Duplicate packets when pinging the ISP gateway.
Dropped packets on the inside interface.
Extremely high latency from the firewall's interfaces, while network core switches maintain normal sub-10ms latency.
Cause:
GlobalProtect Client Misbehavior:
Clients with GlobalProtect enabled caused significant traffic generation even without being authenticated.
Zoom meetings or heavy applications exacerbated the traffic load, creating a near DDoS scenario on the active firewall.
Traffic Looping:
Misconfigured routing or firewall policies caused traffic to loop or flood the data center firewall.
HQ firewall allowed GP clients to directly access the data center in-office, which led to overwhelming traffic bursts.
Infrastructure Context:
HA pair in active/passive mode showed identical symptoms, ruling out hardware issues.
Traffic overload of 300,000 packets/sec was overwhelming the data center's firewall.
Step-by-Step Diagnosis and Resolution
Step 1: Analyze Traffic Flow
Use packet captures on the outside and inside interfaces to identify abnormal traffic patterns.
Identify heavy traffic sources and confirm their origin.
Example: Analyze traffic between HQ clients (GlobalProtect users) and the data center to pinpoint excessive traffic spikes.
Step 2: Debug the GlobalProtect Clients
Check GlobalProtect client logs for repetitive connection attempts or high traffic generation.
If needed, restrict or block GP traffic to the data center while on the HQ network (as implemented in your solution).
Step 3: Prevent Traffic Overload
Traffic Segmentation:
Prevent GlobalProtect traffic from HQ to the data center using a rule or policy, as done in your solution.
Rate Limiting:
Implement rate-limiting rules for GlobalProtect traffic to avoid overwhelming the data center firewall.
Idle Session Timeout:
Configure shorter timeout intervals for GP clients to minimize prolonged traffic issues from inactive sessions.
Step 4: Examine and Optimize MTU/MSS
Adjust MTU and MSS settings for optimal TCP packet handling:
Example: MSS = 1380 and MTU = 1492 can help reduce packet fragmentation issues.
If duplicate packets persist, it could indicate a problem with ISP or physical interfaces.
Step 5: Validate the ISP Connection
Work with your ISP to investigate:
Duplicate packet generation on their gateway.
High latency and packet loss observed on their side of the connection.
Ensure the physical interface between the firewall and ISP is error-free.
Step 6: Monitor and Log High Traffic
Use Palo Alto's logging and monitoring tools:
Identify traffic spikes using App-ID or Zone monitoring.
Enable "GlobalProtect Status" and "System Resources" to identify overload or saturation.
Best Practices for Avoiding Similar Issues
Segregate Traffic:
Use security policies to block or restrict unnecessary traffic between HQ and the data center.
Explicitly define which traffic is allowed to traverse between sites.
GlobalProtect Configurations:
Enable split tunneling to reduce traffic sent to the data center unnecessarily.
Ensure proper client settings to prevent unintended reconnections or excessive authentication attempts.
Rate Limiting and QoS:
Use rate-limiting policies for specific application traffic, especially for bandwidth-intensive apps like Zoom.
Apply Quality of Service (QoS) policies to prioritize critical traffic.
Proactive Monitoring:
Regularly check for unusual traffic patterns using Panorama or other monitoring tools.
Implement automated alerts for high traffic thresholds.
Firewall Resource Allocation:
Ensure adequate hardware sizing for expected traffic loads.
Review firewall session table capacity and resource utilization during peak times.