USG FLEX H Series - IPSec VPN Debug Logging

Zyxel_Claudia

IPSec VPN is a crucial feature for many users of Zyxel security appliances, providing secure connectivity between different sites. However, troubleshooting VPN issues can be challenging with the standard event logs. To address this, uOS now includes detailed IPSec VPN debug logging capabilities.

Key Features

1. Real-Time Trace Logging
   • Command: cmd debug ipsec trace log
   • Function: Provides real-time trace logs, displaying ongoing VPN processes on the console.
   • Usage: Ideal for immediate troubleshooting by capturing logs as events occur.
   • Termination: Use “ctrl + c” to stop the real-time trace logging.
2. Saved Debug Logging
   • Commands:
     • Start Logging: cmd debug ipsec save log
     • Stop Logging: cmd debug ipsec stop log
   • Function: Saves VPN debug logs to a file for extended analysis.
   • File Location: Logs are saved to /tmp/ipsec_vpn.log.
   • Download: Access and download the log file via the firewall’s FTP server.
   • Manage Log Files: Ensure you stop logging when done to prevent unnecessary file growth. The log file size limit is 2 MB, after which older logs are archived.

Debug Logging Procedure

1. Initial Check with Event Logs:
   • Before diving into debug logs, review the event logs to identify the VPN profile and peer IP address involved in the issue.
2. Initiate Debug Logging:
   • Start the real-time trace log with cmd debug ipsec trace log.
   • Alternatively, use cmd debug ipsec save log for saving logging.
3. Trigger the VPN Connection:
   • Manually initiate the VPN connection to generate logs related to the connection attempt.
4. Analyze Debug Logs:
   • Look for logs related to the specific VPN connection.
   • Identify any error messages or keywords that indicate the nature of the problem.

Understanding Debug Log Structure

• Thread ID: Identifies the sequence of related processes within a VPN session.
• Modules:
  • NET: Network-related activities.
  • ENC: Encryption and decryption processes.
  • IKE: Internet Key Exchange protocol management.
  • CFG: Configuration-related tasks.
  • ZLD: Zyxel event logs.

Conclusion

The enhanced IPSec VPN debug logging in uOS provides deeper visibility into VPN processes, enabling more effective troubleshooting. By understanding the structure and key components of debug logs, users can efficiently diagnose and resolve VPN connectivity issues.