Version mismatch on Check Point cluster members may cause traffic loss during an upgradeThis article refers to following DBHA scenario during an upgrade:
Master chassis: upgraded XOS version, upgraded Check Point version
Backup chassis: original XOS version, original Check Point version
The current VRRP Master chassis is already upgraded to a higher XOS version and higher Check Point version. As the next step, the customer upgrades XOS and reloads the Backup chassis. This step can lead to a traffic outage since Check Point application is still at a lower version on the Backup. Cluster members on the Master chassis detect the boot of members at lower version and may switch to "Ready" state (i.e. stop processing traffic despite the chassis itself is VRRP master). This cluster behavior is documented in Check Point SecureKnowledge article sk42096.