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ospf neighbor down

When an ospf neighbor is down, all routes learned form that neighbor are removed from routing table, but all LSAs from that neighbor remain in ospf database till MaxAge.

Anybody explains this. Do you think we need those LSA in our database when the neighbor is unreachable ?

2 REPLIES
Anonymous
N/A

Re: ospf neighbor down

My guess is to restrict the unnecessary transfer of LSA's in case of link flapping.

Bronze

Re: ospf neighbor down

The rules of OSPF, defined in RFC2328, state that only the router that originates a LSA may remove that LSA. Of course, if the router that originated the LSA is no longer reachable, no other router will receive the new LSA with the LS age set to MaxAge.

So, to answer your question, do we need those LSAs in our database? No, but "them's the rules". At least those LSAs are marked as unreachable in the database until MaxAge.

Here's the link to the section of 2328 that explains this.

http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2328.html#sec-14.1

Hope this helps.

Mark

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