OSPF Adjacencies as shown in "show ip ospf interface"

adam-badam-b Member Posts: 36 ■■□□□□□□□□
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,



  • kryollakryolla Member Posts: 785
    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.
    Studying for CCIE and drinking Home Brew
  • adam-badam-b Member Posts: 36 ■■□□□□□□□□
    So then neighbors in the DROTHER state are still considered adjacent?

  • kryollakryolla Member Posts: 785
    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, Area 0
    Process ID 1, Router ID, Network Type BROADCAST, Cost: 10
    Transmit Delay is 1 sec, State DROTHER, Priority 1
    Designated Router (ID), Interface address
    Backup Designated router (ID), Interface address
    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 (Designated Router)
    Adjacent with neighbor (Backup Designated Router)
    Suppress hello for 0 neighbor(s)
    Rack1SW3#sh ip os neigh

    Neighbor ID Pri State Dead Time Address Interface 1 FULL/DR 00:00:31 Ethernet0/1 1 FULL/BDR 00:00:37 Ethernet0/1 1 2WAY/DROTHER 00:00:30 Ethernet0/1
    Studying for CCIE and drinking Home Brew
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