Bug 128629 is what we ran into when upgrading from 8.1.6 to 9.0.5 Only the HA2 HSCI link was down for us. setup a HA2 Backup link. then was able to proceed without interruption. PAN-128269 PA-5250, PA-5260, and PA-5280 firewalls with 100GB AOC cables only Fixed an issue where after you upgraded the first peer in a high availability (HA) configuration to a PAN-OS 9.0 release, the High Speed Chassis Interconnect (HSCI) port did not come up due to an FEC mismatch until after you finished upgrading the second peer.
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