You could create an alert for this one node. Trigger condition = node is up.
If you expect to do this for other nodes, you could introduce custom properties/ groups for your efforts.
Is there a routing protocol (HSRP/ VRRP/ something else) that is involved? Perhaps there is a MIB that can be monitored related to it.
You could configure the router to send traps/ syslogs and possibly catch the event there.