OSPF stuck in EX-START after PAN-OS upgrade

[Param_Upadhyay]

We ran into a situation where the OSPF was stuck into EX-START after upgrading the PAN_OS software from 9.1.10 to 9.1.16 (Preferred release).

We have a deny-all rule above the Intrazone-default allow, but it was working fine previously.

We checked that MTU was not an issue.

We understand from this article - OSPF Neighborship Stuck in Extstart State https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClFBCA0 ,

that we need a firewall rule for the unicast traffic above the deny all and after creating one we saw it started working.

We want to know if someone can help us find the reason why/how was it working before the upgrade without the rule in place?

Thanks

Param Upadhyay

@Didar_Bajwa  @UtkarshKumar 

[UtkarshKumar]

Hi Team

Any help in understanding what could have caused this issue?

[PavelK]

Hello @Param_Upadhyay

The only thing that comes to my mind is following scenario. The OSPF neighborship was established through Intrazone-default security policy first before deny-all security policy was configured. After deny-all security policy was configured, there was no OSPF flap that would trigger OSPF adjacency initiation that would match deny-all until you performed PAN-OS upgrade that caused OSPF adjacency reset hitting deny-all security policy. Would you be able to confirm the life time of OSPF session before upgrade and when deny-all policy was configured?

Kind Regards

Pavel