This article provides information when setting up the configuration of sending syslogs and traps when the syslog/trap receiver server is on a Failover Engine paired with WAN. The public nic on each pair member in a WAN configuration has different IP address than the other, unlike a LAN setup where the addresses are the same.
All versions of FOE with a running WAN config
Have the sending nodes use a primary and secondary ip address to send all syslogs and traps. When the FOE is working properly, the inactive pair member will have syslog service turned off and will reject all traps and syslogs, and the active member will receive the packets and place them into the db as designed.