show ip ospf neighbor

OSPF adjacency state per neighbour — the first stop when routes are missing.

routing

What it does

A healthy adjacency is FULL (or 2-WAY between two DROTHERs on a broadcast segment, which is normal and not a fault). Any other state is a stuck adjacency, and the state names where it stops tell you why.

Per vendor

PlatformCommand
Cisco IOS / NX-OSshow ip ospf neighbor
Juniper JunOSshow ospf neighbor
MikroTik RouterOS/routing ospf neighbor print
FortiOSget router info ospf neighbor

Useful variations

  • Detail for one neighbourshow ip ospf neighbor detail
  • Per-interface OSPF settingsshow ip ospf interface brief

Pitfalls

The misreadings that actually cost people time.

  • Stuck in EXSTART/EXCHANGE is almost always an MTU mismatch between the two interfaces.
  • Stuck in INIT means hellos are one-way — check an ACL or a passive-interface on the far end.
  • No neighbour at all: mismatched area, hello/dead timers, subnet mask, or authentication.
  • 2-WAY between DROTHERs is correct behaviour, not a problem to fix.

Related

show ip routeshow ip interface brief