cluster mode ,one gateway is showing down and another gateway is up , can anyone best analysis

[narnedrak]

this  device vsx  cluster 

cphaprob stat

Cluster Mode: Virtual System Load Sharing (Primary Up)

ID Unique Address Assigned Load State Name

1 (local) 192.168.100.1 0% DOWN CP-FW-1
2 192.168.100.2 100% ACTIVE CP-FW-2

Active PNOTEs: FSYNC, ADMIN

Last member state change event:
Event Code: CLUS-112600
State change: INIT -> DOWN
Reason for state change: FULLSYNC PNOTE - SIC failure
Event time: Thu May 9 19:41:42 2024

performed 

cpstart;stop

sic reset (established but CP 1 is down )

[PhoneBoy]

This exact message is described here: https://support.checkpoint.com/results/sk/sk145372
Sounds like an MTU issue on your switch.