From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Fri Oct 03 2003 - 11:05:02 GMT-3
At 9:50 AM +0100 10/3/03, Ken.Farrington@barclayscapital.com wrote:
>Work question here. - sorry if not appropriate to the forum.
>
>If you have 6 equal cost paths to a destination, and you have in IGRP/EIGRP
>or OSPF the default max-paths set to 4.
>
>Which 4 paths does the routing table pick to be entered into the routing
>table.
>
>Is it based on neighbour IP?
>
I'm reasonably certain that it simply accepts the first four eligible
paths presented to the routing table installation process, and simply
ignores other potential paths unless one or more of the first four
goes down. Remember that the final decision on load balancing is in
the routing table installation process, not any specific routing
protocol.
BGP, to some extent, is an exception, since it specifically selects
best path unless you enable maximum-paths. There are special cases
in IGPs that have a concept of external routes -- when last checked,
OSPF deliberately will not install equal-cost externals on a specific
router. That doesn't mean that a default routes of external type I
won't get advertised with the same initial cost, but that a router
will pick only one of them.
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