When the VPN Isn't the Problem
  

George Fady Lv2Posted 2026-Jul-24 15:35

Following up on my previous post, the investigation revealed that the VPN itself was working exactly as expected.
The real issue was a misconfigured Security Policy.
The rule intended to allow LAN → VPN traffic had its source and destination zones reversed. As a result, outbound traffic never matched an allow rule and was dropped by the default deny policy before it could even enter the IPsec tunnel.
After correcting the policy:

  • Bidirectional communication was restored.

  • Traffic was successfully encrypted and decrypted.

  • The customer confirmed that connectivity was fully restored.

This case is a good reminder that not every VPN issue is caused by Phase 1 or Phase 2 negotiation failures. Once the tunnel is established, the next areas to verify should always be:
• Security Policies
• NAT Rules
• Route Selection
A systematic troubleshooting approach not only reduces resolution time but also avoids unnecessary changes to a working VPN configuration.
Have you encountered a similar case where the VPN was healthy, but another component was preventing traffic from passing?

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Humayun Ahmed Lv4Posted 2026-Jul-24 17:19
  
Thanks to share!
Eiko Lv2Posted 2026-Jul-24 15:43
  
Great topic!