OSPF Adjacency Formation

In this short and simple blog I will show you the steps it takes for two routers to form OSPF adjacency. Though we might have read about it in books but this debug output will show each step and strengthen your understanding.

Debug ip ospf adj
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Cannot see ourself in hello from 3.3.3.3, state INIT
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Neighbor change event
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: DR/BDR election
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Elect BDR 0.0.0.0
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Elect DR 1.1.1.1
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: DR: 1.1.1.1 (Id) BDR: none
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: 2 Way Communication to 3.3.3.3, state 2WAY
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Neighbor change event
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: DR/BDR election
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Elect BDR 3.3.3.3
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Elect DR 1.1.1.1
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: DR: 1.1.1.1 (Id) BDR: 3.3.3.3 (Id)
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Nbr 3.3.3.3: Prepare dbase exchange
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Send DBD to 3.3.3.3 seq 0x1048 opt 0x52 flag 0x7 len 32
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Neighbor change event
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: DR/BDR election
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Elect BDR 3.3.3.3
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Elect DR 1.1.1.1
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: DR: 1.1.1.1 (Id) BDR: 3.3.3.3 (Id)
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Neighbor change event
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: DR/BDR election
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Elect BDR 3.3.3.3
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Elect DR 1.1.1.1
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: DR: 1.1.1.1 (Id) BDR: 3.3.3.3 (Id)
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Rcv DBD from 3.3.3.3 seq 0x1D81 opt 0x52 flag 0x7 len 32 mtu 1500 state EXSTART
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: NBR Negotiation Done. We are the SLAVE
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Nbr 3.3.3.3: Summary list built, size 4
*Feb 25 22:30:42.565: OSPF-1 ADJ Et0/1: Send DBD to 3.3.3.3 seq 0x1D81 opt 0x52 flag 0x2 len 112
*Feb 25 22:30:42.566: OSPF-1 ADJ Et0/1: Rcv DBD from 3.3.3.3 seq 0x1D82 opt 0x52 flag 0x1 len 32 mtu 1500 state EXCHANGE
*Feb 25 22:30:42.566: OSPF-1 ADJ Et0/1: Exchange Done with 3.3.3.3
*Feb 25 22:30:42.566: OSPF-1 ADJ Et0/1: Synchronized with 3.3.3.3, state FULL
*Feb 25 22:30:42.566: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Ethernet0/1 from LOADING to FULL, Loading Done
*Feb 25 22:30:42.566: OSPF-1 ADJ Et0/1: Send DBD to 3.3.3.3 seq 0x1D82 opt 0x52 flag 0x0 len 32
*Feb 25 22:30:42.566: OSPF-1 ADJ Et0/1: Rcv LS REQ from 3.3.3.3 length 72 LSA count 4
*Feb 25 22:31:22.571: OSPF-1 ADJ Et0/1: Nbr 3.3.3.3: Clean-up dbase exchange

I hope this helps better understanding the steps involved during OSPF adjacency.

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