Troubleshooting Tip: VPN IPsec are down cause iked UDP ports 500 and 4500 was taken by another process

[jcastellanos]

Description	This article describes how to diagnose a random scenario where the VPN IPsec cannot come up cause the ports 500, and 4500 were assigned to another process different from the iked.
Scope	FortiGate v6.4.x.
Solution	Run an ike debug but not display information: diagnose debug application ike -1 diagnose debug enable Try to reboot the iked process, the issue is not fixed, a message mentioning that port 4500 is used can appear: Run the command and see if port 4500 is used by another service: diagnose sys udpsock Possible workarounds: Make a failover of the slave in case you are in HA topology. Reboot the FortiGate with the issue. The UDP ports 500 and 4500 are assigned to iked process when VPN IPsec is not under this scenario.