From: OhioHondo (ohiohondo@columbus.rr.com)
Date: Sat Mar 22 2003 - 20:04:07 GMT-3
Richard
Local Preference is used by iBGP routers to co-ordinate their interface to
ouside AS's. If you have 2 BGP routers learning external routes, they share
this knowledge with one another via iBGP. If they both have learned a route
to a given prefix, the question comes up --- which BGP router should the
local AS use to reach the external prefix --- which will be the egress point
for the local AS. Manipulating Local_Preference on prefixes learned from
external sources allows the iBGP routers to come to a common decision on
where the preferred egress pont is to get to each external network.
Some attributes are used to manipulate egress points for your AS. Some are
used to manipulate (try to influence) ingress points. MED and prepending to
the AS_PATH are attempts to influence the ingress point to your AS that
other AS's use to get to prefixes/networks in your AS.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Richard Davidson
Sent: Saturday, March 22, 2003 3:24 PM
To: groupstudy
Subject: bgp local-preference Q.
Hello All,
On one router R5 I have a route-map with a local
preference of 101 and have mapped that to an IBGP
neighbor R6. This router (R5) only changes the local
pref. for routes that it has learned via EBGP (R7).
Does any one know why the only the EBGP learned routes
get the local pref. changed? Any ideas or links would
be helpful.
This is in a lab from IPexperts.net section 9 task 12
if anyone has the same lab.
Thanks
Richard Davidson
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