A neighbor shows up in INIT and never moves on. What does that mean?
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INIT means I receive the neighbor's hellos but my router ID is not in them, so it does not hear me. The problem is in one direction: an ACL or firewall dropping protocol 89 one way, a unidirectional link, multicast filtering on a switch in between, or on NBMA a map without broadcast support.
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Reasoning
The 2-Way check is "my router ID appears in your hello". If R1 sees R2 in INIT, R2's hellos reach R1 but R1's hellos do not reach R2, or R2 discards them.
What to check
- ACLs and firewalls inbound on R2 or along the path: they must permit IP protocol 89 to
224.0.0.5. - The link itself: a fiber with one bad strand, shown by input errors or UDLD on a switch in between.
- Multicast handling on a switch or wireless bridge between the routers.
- NBMA or hub-and-spoke clouds: one side has no mapping that carries multicast or broadcast.
Proof
R2# debug ip ospf helloIf R2 shows nothing from R1 at all, the hellos are not arriving. A capture or an ACL with log on R2's
interface tells you if they arrive and get dropped.
They will ask next
Why does authentication mismatch rarely show as INIT on both sides?
Usually both sides drop each other's hellos, so neither lists the other and you see no neighbor at all. INIT appears when only one side's packets are rejected.
Traps
- Changing timers or areas. Those would stop hellos from being accepted at all, not leave the neighbor in INIT.