GRE Tunel not working after 7.4.1 > 7.4.3

[itc]

Hi

My GRE tunel connection is not working after upgrade FortiOS from 7.4.1 > 7.4.3.

Forti shows, that connection is UP but I have no access  to network. 

Checked policies, diagnosed connection and everything looks fine.

Any idea what to check next? How to monitor?

Best regards,

Rafal

[rtanagras]

Hi @Rafal - You can try disabling "np-acceleration" and "auto-asic-offloading" to troubleshoot the issue. Additionally, examining the sniffer output and using the debug flow command can provide more insights.

[hbac]

Hi @itc,

Are you using NAT? Are there any IP pools/VIPs related to local/remote subnets of the GRE tunnel? There was a behavior change on the new version which might cause the issue. Please refer to https://community.fortinet.com/t5/FortiGate/Technical-Tip-IP-pool-behavior-Change-in-default-ippool/...

Regards, 

[infor1]

I have the same problem. Have you solved the problem?

[AEK]

Try follow @rtanagras and @hbac suggestions.

[infor1]

I used it, but it helped. I had to go back to the old firmware. The old one works ok.

in log knowledge this :
anti-spoof check failed,drop

[Deltaman]

Hi,

I have the same issue and have made a case.

GRE Tunnel not working after 7.4.1 > 7.4.2 or 7.4.3. Roll back solves the issue

With diagnose sniffer I can see that traffic is only inbound and not outbound. Interfaces show status up, but traffic is not encapsulated when needs to go outbound.

Also I have seen that the route for data that should travel through the GRE tunnel is not installed when running firmware 7.4.2 or 7.4.3.

Regards,

Hugo

[AEK]

Hi Hugo

That's interesting info.

Did you try manually install the missing route to see if it fixes the issue?

[Deltaman]

Yes I did, but the routes does then also not get installed, then you would think that the interface is not up what causes the route to be not installed.

But GUI displayes as interfaces are all up.

[AEK]

Another interesting piece of the puzzle. Can you try remove the GRE interface and create it again the reinsert the route?

Also can you share gre interface properties:

show full sys interface greX

And routing DB:

get router info routing-table  (share only relevant entries)