Just recently changed the Orion server IP and ran into a few issues.
Issue 1. Massive device outage alert emaisl sent to everyone. Be sure to turn off the alerting engine and set it to manual if you don't want your boss calling you or at leat notify everyone prior to the change. Turn it back on once the application is working and seeing all the managed devices.
issue 2. A large number of devicse will be shown as UNKNOWN. Restart SNMP service and this will resolve the issue
Issue 3. Some devices still shown as UNKNOWN even after restarting the SNMP and rescanning monitoring resources. I had to deleted the node and re-add it back, historical data will be lost.
I hope this is helpful