From: Peter van Oene (pvo@usermail.com)
Date: Sat Mar 01 2003 - 19:36:59 GMT-3
At 04:15 AM 3/1/2003 +0000, Sage Vadi wrote:
>Guys,
>
>I am talking about OUTGOING metrics. I am well aware
>of manipulating interface metrics and AD: they are
>LOCALLY significant - as testing in my lab proves.
Routers in a link state network calculate minimal, or least cost paths
through the spanning tree based upon a unidirectional cost. In your
example below, A has a cost to use the A-B network, and B has a
cost. However, A is only concerned with its own cost to use the
link. Hence, any path determination done by A that includes network A-B
will only include A's cost for the link. In this way, it is normal for
A's cost to B to be different from B's cost to A.
With this in mind, I'm not entirely sure what you are asking. A cannot
tell B how expensive the network is between them as A does not share B's
perspective. A larger lab would likely prove more illustrative of link
state traffic engineering concepts using link metrics.
>A----B
>
>How do I modify the outgoing routes of A, on A ITSELF.
>Not on B, where obviously these methods can be easily
>applied.
If you want B to change its opinion of the A-B link, you need to work on
router B.
>Q) Is this possible @ all? The ISIS design guide does
>not state anything about this. I would think that with
>such a procotol as ISIS surely we would have a
>possible tweak in this manner?
OSPF does this in the same way. Try looking through rfc2328 for some
examples. For more info, try searching around the net for terms link
minimal spanning trees, weight digraphs and similar.
>rgds,
>Sage
>
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