Re: Decrease size of Syslog & SNMP to avoid going over IPSEC MTU
First, change the mode of syslog from UDP to TCP,
# config log syslogd setting
# set mode reliable
What I would suggest is that you can try to change the tcp mss value in the policy for the VPN traffic. Try matching the Syslog messages only in that policy for testing.
# config firewall policy
# edit <Policy ID>
# set tcp-mss-sender 1000
# set tcp-mss-receiver 1000
Let me know if that works or not.