All OSPF neighbors suddenly down

[JMBerzal]

Hello all,

Customer has a problem were their PaloAlto suddenly declares all neighbors adjacencies down, after that the PaloAlto will do a grateful restart and the OSPF neighbors will change to init, and then go full again, this OSPF flapping lasts 15 seconds or so so there is nearly no service impact at all, but customer would like to understand why is this happening and how to avoid it.

I think the problem is related to the PaloAlto because the OSPF adjacency is lost at the exact same time for all neighbors, even though half of the neighbors are in separate interfaces and separate virtual routers, with different OSPF configuration. 

The problem has happened 3 times on the last month but the system logs only show declaring the neighbor down and the grateful restart afterwards. Is there any way to troubleshoot the issue after it happened? The routerd.log are no longer showings logs for that day...

The FW is a PA-5050, with version 8.1.21

Thank you in advance,

Jose

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