Question

Two IOS-XR routers, R1 and R2, are directly connected on a point-to-point link and configured for OSPFv3 to exchange IPv6 routes. R1's interface is configured with 'ospfv3 1 ipv6 area 0' using the default instance ID, while R2's interface was manually set with the command that specifies instance ID 64. Both interfaces are up/up, IPv6 link-local addresses are reachable, and MTU matches. However, the OSPFv3 adjacency never forms and remains in the DOWN/INIT state. What is the most likely cause?

Accepted Answer

The OSPFv3 instance IDs in the Hello packets do not match, so each router silently discards the other's Hellos and no adjacency forms

Answer

OSPFv3 requires global unicast IPv6 addresses on the interfaces; link-local addresses alone cannot establish adjacency

Answer

The routers have mismatched OSPF process IDs (1 vs 64), which must match for neighbors to peer

Answer

IPv6 unicast routing is disabled on one router, preventing the OSPFv3 database exchange