When does an OSPF router become an ABR?
- when the router has interfaces in different areas
- when the router is configured as an ABR by the network administrator
- when the router has the highest router ID
- when the router has an OSPF priority of 0
Explanation: When a router has interfaces connected to different areas, it becomes an ABR without requiring extra configuration. The router ID and priority values determine DR/BDR status.