After upgrade to 7.2.6 or 7.4.1 wan interface is flapping

[gkats]

I have a FortiGate 40F and at 7.2.5 everything was working properly. After the upgrade to 7.2.6, the same problem exists on 7.4.1, the wan interface (PPPoE) is failing. After a few seconds it is getting the IP from the ISP but almost immediately it fails again and is getting the 0.0.0.0/0.0.0.0

Are there any suggestions?

FortiGate 

[kumarh]

Can you connect a laptop directly to wan interface, assign ip to the interface and then start a constant ping and see if the interface flips again.

[gkats]

On this interface (wan) there is the ISP modem. This acts as a DHCP, so when I manually entered an IP of this local network 192.168.1.x it worked. Of course with the DHCP as well, since the IP is within this specific network range. After changing it back to PPPoE, it has the same behavior as described in the ticket.

[hbac]

Hi @gkats, 

Debug will be useful. Please follow this article to collect debugs while it is flapping: https://community.fortinet.com/t5/FortiGate/Technical-Tip-Troubleshooting-PPPoE-connection-failed/ta...

Regards, 

[BillH_FTNT]

Hi @gkats , What is your system status now ? Did you try debug messages follow a guide from @hbac post ?

[gkats · Accepted solution]

Thank you very much for the guide and the support @hbac . I run the commands and after trying also many things like reset, rollback etc it turned out that the issue was related with an auto provision policy that was recently forced by the ISP. Changes were made from their end and the issue was resolved.