This command tells OSPF to communicate with unicast updates to a specific neighbor. This is particularly useful over non-broadcast links, such as frame-relay, as adjacenies will not form by default.
Router(config-router)#neighbor <ip address>
In this example, we will configure R4 to send its updates to R3 using unicast. First, we’ll configure OSPF on R1, R3, and R4 for all interfaces.
R4(config-router)#router ospf 1 R4(config-router)#network 0.0.0.0 0.0.0.0 area 0
After a couple minutes R4 still doesn’t have any adjacencies.
R4(config-router)#do show ip ospf neighbor R4(config-router)#
Notice that the OSPF network type is non_broadcast, so it will require unicast updates.
R4(config)#do show ip ospf interface s0/0 Serial0/0 is up, line protocol is up Internet Address 10.4.4.4/24, Area 0 Process ID 1, Router ID 220.127.116.11, Network Type NON_BROADCAST, Cost: 64 Transmit Delay is 1 sec, State DR, Priority 1 Designated Router (ID) 18.104.22.168, Interface address 10.4.4.4 No backup designated router on this network Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5 oob-resync timeout 120 Hello due in 00:00:25 Supports Link-local Signaling (LLS) Index 1/1, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0, maximum is 0 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 0, Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s)
After we configure the neighbor statement, the adjacencies come up.
R4(config)#router ospf 1 R4(config-router)#neighbor 10.4.4.1 R4(config-router)#neighbor 10.4.4.3 R4(config-router)# *Mar 1 00:45:55.347: %OSPF-5-ADJCHG: Process 1, Nbr 22.214.171.124 on Serial0/0 from LOADING to FULL, Loading Done *Mar 1 00:45:55.359: %OSPF-5-ADJCHG: Process 1, Nbr 126.96.36.199 on Serial0/0 from LOADING to FULL, Loading Done