In addition to the EEM Failover Configuration and Failover Tool usage documented below:
What are the port requirements between EEM nodes?
What mechanism does EEM use to recover data when there is an outage of one of the nodes?
EEM uses port 509 by default to communicate between nodes. This is specified during installation and can be configured post-install in the '$DXHOME/config/knowledge/itechpoz.dxc' file by modifying this line:
snmp-port = 509
The port communication must be bidirectional between EEM nodes.
When one of the EEM nodes becomes unreachable or unavailable, the remaining EEM nodes can replicate, even if the missing EEM is the Primary server. The remaining EEM nodes store any updates in their local database files and when the missing EEM node becomes available again, they propagate any changes using a proprietary internal multi-write mechanism.