We will use below topology and different subnet at both end, then we will check the adjacency and try to ping in order to confirm.
R2 F0/0 <—–> F0/0 R3
R2#sho run int f0/0 Building configuration... Current configuration : 153 bytes ! interface FastEthernet0/0 no ip address duplex auto speed auto ipv6 address 2001:2::2/64 ipv6 address FE80::2 link-local ipv6 ospf 1 area 0 end
R3#sho run int f0/0 Building configuration... Current configuration : 153 bytes ! interface FastEthernet0/0 no ip address duplex auto speed auto ipv6 address 2001:3::3/64 ipv6 address FE80::3 link-local ipv6 ospf 1 area 0 end
Checking routes on R2:
R2#sho ipv6 ospf ne Neighbor ID Pri State Dead Time Interface ID Interface 22.214.171.124 1 FULL/DR 00:00:35 4 FastEthernet0/0 R2#sho ipv6 route IPv6 Routing Table - 5 entries Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP U - Per-user Static route I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2 ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2 C 2001:2::/64 [0/0] via ::, FastEthernet0/0 L 2001:2::2/128 [0/0] via ::, FastEthernet0/0 O 2001:3::/64 [110/10] via ::, FastEthernet0/0 L FE80::/10 [0/0] via ::, Null0 L FF00::/8 [0/0] via ::, Null0
Trying to ping 2001:3::3 from R2:
R2#ping 2001:3::3 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2001:3::3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 8/20/56 ms R2#
Adjacency is establishing and able to ping because neighbors are known by their router-ids. Link-local addresses are used as next-hops, not actual interface address.