OSPF neighbor states
During the OSPF adjacency formation process, two OSPF routers transition through several states, which include:
- Down- first OSPF neighbor state in this state no information (hello) has been received from the neighbouring router but in the down state hello packets can be sent to the neighbor.
- Attempt- this state is only valid for manually configured neighbor in an non broadcast multi-access (NBMA) environment. router send unicast hello packets every interval to the neighbor orm which hello's have not been received within the dead interval.
- Init-OSPF router recieved a hello packets from its neighbor but the receiving router's ID was not include in the hello packets.
Configure Router ID-
R1(config)#router ospf 1
A.B.C.D OSPF router-id in IP address format
4. 2 WAY- 2 way state is attained when the router receiving the hello packets and router seen its own router ID within the received hello packet. Bidirectional communication has been established. In the broadcast multi-access networks, an election can occur after this point.
5. Exstart- the actual process of exchanging link states information can start between the OSPF routers. master/slave relationship is established and initial sequence numbers are exchange.
6.Exchange- In the Exchange state, OSPF routing information is exchanged using Database description (DBD or DD) packets and link-state request (LSR) and link state update (LSU) packets may also be sent. In this state OSPF router see what LSA's they have and what LSA's they do not have.
7.Full- In the full state, all LSA's information is synchronized among neighbors and adjacency has been established.
%OSPF-5-ADJCHG: Process 1, Nbr 184.108.40.206 on Serial3/0 from LOADING to FULL, Loading Done
R1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
220.127.116.11 0 FULL/ - 00:00:39 18.104.22.168 Serial3/0
Before we start BGP configuration check out some important of BGP CCIE exam topics.
Here are the lists of all OSPF labs and theories CCNA to CCIE.
7.Routing Protocol Authentdication (RIP, and OSPF)
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