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Cisco · Cisco IOS XE

Cisco OSPF Show Commands: Neighbors, Interfaces and Missing Routes

Quick answer #

Inspect OSPF neighbors and interfaces together. First establish whether the expected adjacency exists; only then investigate the link-state database and installed route. Full means the adjacency synchronized, not that every expected destination must appear in the routing table. On a broadcast network, 2-Way can be normal between two DROTHER routers.

Scope: OSPFv2 IPv4 on IOS XE, including IOS XE 17.x routing platforms. The examples use the global context. OSPFv3, multiple process IDs and VRF-specific syntax need their own context and are not interchangeable with these commands.

Read-only commands #

Read-only commands
Cisco IOS XE · Authorized EXEC mode; context specified below

Read-only
show ip ospf
Read-only
show ip ospf neighbor
Read-only
show ip ospf neighbor detail
Read-only
show ip ospf interface brief
Read-only

Replace these example values: GigabitEthernet0/0/0.

show ip ospf interface GigabitEthernet0/0/0
Read-only
show ip ospf database
Read-only
show ip route ospf
Read-only

Replace these example values: 203.0.113.25.

show ip route 203.0.113.25

Workflow #

  1. Record the expected neighbor, local interface, area and process. Router IDs and interface addresses have different roles, so retain both rather than assuming they are identical.
  2. If the expected neighbor is absent, inspect the interface at both ends. Compare addressing, area, network type, hello/dead timers, authentication configuration and whether the interface is passive.
  3. If the neighbor repeatedly stalls during database exchange, compare interface MTUs and the surrounding transport. Preserve state transitions and relevant logs before changing anything.
  4. If the adjacency is Full, inspect the database for the affected destination's advertisement and then inspect the selected route. A healthy neighbor relationship does not prove the remote router originated the intended network.
  5. Compare the return route and forwarding path once the prefix is installed. This avoids spending the entire investigation on OSPF when the actual failure is farther along the service path.

Read neighbor states carefully #

Init means the router has seen a hello but has not established bidirectional visibility with that neighbor. ExStart and Exchange concern database-description exchange; an MTU mismatch is a possible cause of a persistent stall, not the only one. Loading concerns obtaining needed link-state information. Full is the expected synchronized state for adjacencies that should become fully adjacent.

Do not treat every 2-Way entry as broken. On broadcast networks, DR/BDR election affects which routers form full adjacencies. Compare the network type and the routers' roles before investigating a normal relationship as a fault.

Evidence to save #

Save neighbor detail and the corresponding interface output from both sides. Include the affected destination and whether it is missing from the database, absent from the routing table or installed but unreachable. These are separate failure locations with different next steps. Avoid resetting the OSPF process or bypassing MTU checks as an initial diagnostic action.

Useful tools and references #

  • MTU budget calculator: Account for transport encapsulation when investigating an adjacency that stalls during database exchange.
  • IPv4 subnet calculator: Check the local and peer interface address ranges while comparing their link configuration.

Sources

Documentation reviewed: 8 October 2026