Network & Infrastructure / OSPF & Underlay Convergence
OSPFv3 link-local next hops and incomplete IPv6 troubleshooting
An IPv6 route points to a link-local next hop that an engineer mistakes for an unusable address. A separate neighbor-discovery issue may be the actual forwarding failure.
Environment and inputs: OSPFv2 IPv4 underlays, with OSPFv3 explicitly identified where used; timers and diagnostics vary by platform. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Record OSPFv3 neighbors, interface scope, link-local addresses and IPv6 neighbor entries. Include the outgoing interface whenever comparing or testing a link-local next hop.
Explain the result
Link-local addresses are scoped to a link and are normal next-hop identifiers in IPv6 routing. The same textual address on different links does not identify one globally unique neighbor.
Plan the fix
Validate the correct scoped adjacency and repair neighbor discovery or interface association when evidence shows failure. Avoid replacing link-local next hops with arbitrary global addresses.
Check the result and rollback
Test forwarding through each expected egress interface and confirm stable neighbor state. Revert if configuration changes create duplicate address ownership or disturb router-advertisement behavior outside the underlay.