site-to-site VPN tunnels, which are going up and down after upgrading from version 6.4.15 to 7.2.8

[ghbhaddar1]

First, I thank the community members for their quick responses. After checking the cluster, I noticed an issue with the site-to-site VPN tunnels, which are going up and down after upgrading from version 6.4.15 to 7.2.8. Does anyone have insights or tips on how to fix this

[mriswan]

Could you please provide more info about the tunnel or tunnels? And how frequently the tunnel is flapping.

diagnose vpn ike gateway list name <IPsec remote gateway name>

diagnose vpn tunnel list name <IPsec tunnel name>

[bkrishnan]

Provide the output of the below command when you are facing the issue
diagnose debug application ike -1
diagnose debug enable

https://community.fortinet.com/t5/FortiGate/Troubleshooting-Tip-IPsec-flapping-or-packet-loss-after-...