Re: OSPF route selection

From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Tue May 11 2004 - 16:15:25 GMT-3


At 6:07 PM +0300 5/11/04, Dan wrote:
>Hello all,
>
>I searched the archive and found no answer:
>
>How does OSPF selected routes from its database?
>Does it prefers LSA X over LSA Y? or is the cost is have ultimate preference?
>Are LSA 5/7 considered as inter-area or intra-area?

They are considered external.

>
>Could you point me to the relevant url?
>

(URL eater food)

The OSPF working group official page is
http://www.ietf.org/html.charters/ospf-charter.html

This will give you the current standard:
http://www.ietf.org/rfc/rfc2328.txt Other documents will give you
some special cases.

The basic rule:
    Always prefer intra-area over inter-area over external 1 over external 2.
    Within a category, take the longest match.
    To break ties with equal match length, use route cost.
    If there are still ties, load-share up to the configured limit of
parallel routes.



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