From: David Timmons (masterdt@yahoo.com)
Date: Wed Jul 12 2006 - 14:58:39 ART
Hi,
Have been thinking about BGP clusters and wonder about
Router Reflectors (RR) and the redundancy issues. I
noticed that IOS RR clients later then 12.0 can
understand two major attributes: originator_ID and
cluster_list. So, so you can get the client to help
prevent loops rather then using the cluster_ID.
(RR x)--
| <IBGP AS 1>--(RR Client)--<AS 1 to As 2>-ISP
(RR y)--
For example, if a route is injected into bgp AS 2 via
an ISP router and arrives at our RR client, then it
gets advertised to both RR routers. The result will be
that the RR could have two routes to the ISP. If
router x prefers path to router y, x will withdraw
route sent to router y. X will also send an update to
the RR Client; however, the RR client will not allow
the update because the originate_id was set to the RR
client.
So, I don't understand why we would prevent routing
loops with RR redundant designs by setting the
cluster_ID. From some of the examples that I have been
working on, it appears that that it is better to
configure distinct cluster_ID's on the RR.
dt
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