From the release note for Robot 5.30:
"Added validation of specified robotip against known local interfaces, with alarm and reversion to last known good ip on error. Add 'local_ip_validation = no' if you need to turn off this functionality."
This functionality was added because of the situation which arises if the robot is misconfigured with the ip of another robot. This would create problems which where rather difficult to track down. With the added check the misconfiguration would be immediately detected. As you can see you can turn it off to get back the old behaviour.
Regards, Koert