OSPF - Identifying the router type

In OSPF networking, you can determine the type of a router using the show ip ospf command on Cisco devices. The output will indicate whether the router is an internal router, an area border router (ABR), or an autonomous system boundary router (ASBR).

  • Internal Router: Operates within a single OSPF area.
  • Area Border Router (ABR): Connects multiple OSPF areas, which can be identified by verifying if the OSPF configuration features interfaces in more than one area.
  • Autonomous System Boundary Router (ASBR): Interfaces with at least one network outside the OSPF domain, typically detected by the presence of an interface not engaged in OSPF.

Example output snippet:

Router# show ip ospf 1
 Routing Process "ospf 1" with ID 10.0.0.1
 ...
 It is an autonomous system boundary router
 ...

Alternative methods to identify router types:

  1. Area Border Router (ABR): Check the OSPF configuration for interfaces in more than one area.
  2. Autonomous System Boundary Router (ASBR): Look for at least one interface not participating in OSPF.

These methods provide quick ways to determine the OSPF router type without relying solely on the show ip ospf command.