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

[AEK]

Hello @kaskipl 

anti-spoof check fail means the FG doesn't have route back to the sending IP. I think GRE is somehow not pushing the route to the routing table.

Can you try add manually the related static route to the FG once GRE is established?

[kaskipl]

Thank you for your response @AEK .

This is what I did in one of my attempts to solve this problem.

Unfortunately, adding a static route doesn't change anything.

Regards

[Kangming]

Thank you, Kaskipl.

Are both ends of GRE site FGT-VM?

If you could share your configuration file, it would be conducive for us to reproduce the issue.  My email is: kmliu@fortinet.com

[kaskipl]

Hello @Kangming 

Unfortunately, I don't know which vendor my telecommunications operator uses.

If it's important information, I'll try to get it

I will try to generate a ticket on Monday.

I understand that the objects related to this tunnel are enough from the configuration?

Regards

[Glennonline]

I'm having the same issue, is it worth the effort to create a ticket?

[pginete]

Hi Team,

Good day! If the traffic over GRE tunnel stops working after upgrading to 7.4.3, kindly run the command below three times.

diag sys gre list

If the collisions of the GRE tunnel are increasing, then it matches bug 987501.

You may check this KB https://community.fortinet.com/t5/FortiGate/Troubleshooting-Tip-GRE-traffic-stops-working-after-a-fi...for workaround and solution.

Thank you.