Event log message 'SGRP Admin: can't determine interface ip address, using first IP address'
You want to understand the event log message 'SGRP Admin: can't determine interface ip address, using first IP address'

This event log message happens when you configure a failover group with a group-id that does not belong to any subnet that the ProxySG belongs to. In other words the ProxySG does not have any interface IP address that corresponds to this failover group. So failover is going to just use the first configured IP address, typically the IP address of interface 0. The failover advertisements will be sent on this interface.