Adjacency in OSPF

Unanswered Question
May 31st, 2007

Hello i m athar.

I want to know that what r the adjacent routers in OSPF.or what is an adjacency relationship.

Can directly connected routers only have this type of relationship in ospf or not?



I have this problem too.
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devang_etcom Thu, 05/31/2007 - 08:33


In OSPF both the router on ths same link will exchange their parameters with each othere to aggree upon some set of requirements like area id, holdtime, hello timer, network type as well as their identification using router id... if both the neighbor will aggreed with those paramters then they will start exchanging routing table and updates with each other...

and if both the neighbor will have different set of parameters then they will not be neighbor of each othere and there is no any exchange between both the routers...



Richard Burts Thu, 05/31/2007 - 08:38


As Devang points out first OSPF routers must form a neighbor relationship, which is accomplished when a set of parameters match correctly. After the routers become neighbors they must decide whether to form an adjacency. Adjacency is established when they have exchanged the content of their Link State Data Base with each other. When they have completed the exchange of their LSDB they know that they are in sync with each other and that their LSDBs match exactly. This is the most important aspect of adjacency - if the LSDB match exactly then when they draw the map of the topology of the network then they will each draw the same map. This is an important part of loop avoidance in OSPF that the maps will match so that they will not produce a loop.



bvsnarayana03 Thu, 05/31/2007 - 22:37


When router exchnge HELLOs they are called neighbors.

When routers exchange Link state database they are called adjancies.

All adjancies are neighbors, but all neighbors are not adjancies.

Richard Burts Fri, 06/01/2007 - 11:31

This is a very nice way to lay out the relationship between these terms. Nicely done.




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