OSPF Adjacencies as shown in "show ip ospf interface"

adam-b

Hello Guys,

The BSCI Exam guide on p. 148 Example 5-5 shows the output of the "show ip ospf interface fastethernet 1/0" command. The output states "Neighbor Count is 3, Adjacent neighbor count is 2." Yet it also lists three neighbors as being "adjacent." Can someone please explain this what-seems-to-be contradiction? What does "adjacent" refer to in this output? It was my assumption that a router could only be ajacent with the DR and BDR.

Any insight is appreciated.

Thanks Guys,

Adam

kryolla

you can only be at a full state with the DR and BDR but neighbors with DRothers which will stop at 2 way and will not be at a full state.

adam-b

So then neighbors in the DROTHER state are still considered adjacent?

Thanks.

kryolla

according to sh ip os int xxx it does not form adjacency but you do form neighbors. So I guess the book can be a little misleading in saying that all 3 neighbors are adjacent

Rack1SW3#sh ip os int e0/1
Ethernet0/1 is up, line protocol is up
Internet Address 155.1.146.9/24, Area 0
Process ID 1, Router ID 150.1.9.9, Network Type BROADCAST, Cost: 10
Transmit Delay is 1 sec, State DROTHER, Priority 1
Designated Router (ID) 150.1.1.1, Interface address 155.1.146.1
Backup Designated router (ID) 150.1.4.4, Interface address 155.1.146.4
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:00
Index 4/4, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 1
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 3, Adjacent neighbor count is 2
Adjacent with neighbor 150.1.1.1 (Designated Router)
Adjacent with neighbor 150.1.4.4 (Backup Designated Router)
Suppress hello for 0 neighbor(s)
Rack1SW3#sh ip os neigh

Neighbor ID Pri State Dead Time Address Interface
150.1.1.1 1 FULL/DR 00:00:31 155.1.146.1 Ethernet0/1
150.1.4.4 1 FULL/BDR 00:00:37 155.1.146.4 Ethernet0/1
150.1.6.6 1 2WAY/DROTHER 00:00:30 155.1.146.6 Ethernet0/1
Rack1SW3#