From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Fri Apr 02 2004 - 20:09:13 GMT-3
At 5:52 PM -0500 4/2/04, Peter van Oene wrote:
>ATHIS IS WHAT I AM NOT UNDERSTANDING. CAN SOMEONE HELP CLARIFY> ARE THEY
>>REFERRING TO ROUTEMAPS ON THE CLIENT OR THE RR. IF CLIENT, What if
>>the client
>>has an IBGP peer other than the RR. I know it is not a good design
>>to do that but I have seen scenerios that ask for it, and we know
>>the LAB is not a best practice lab.
>
>The below refers to the changing of BGP attributes on a Route
>Reflector, not the server. Further, meshed RR clients are not
>necessarily bad. Do you have a situation where you want to change a
>BGP attribute within your IBGP mesh?
Actually, meshing clusters is often best current practice, unless you
know EXACTLY what you are doing. See
http://www.ietf.org/rfc/rfc3345.txt on the "Border Gateway Protocol
(BGP) Persistent Route Oscillation Condition." This is worth reading
just to understand the pros and cons of meshing within a cluster, and
when it is safe not to do it -- or what precautions you need to take
when doing it under certain specific conditions, such as hierarchical
route reflectors.
If you read and think about the concepts in RFC 3345, you will learn
a good deal about why, for example, OSPF _always_ prefers intra-area
routes.
>
>
>>===============================================================================
>>If a set clause is used to modify an attribute, a routing loop may
>>occur when the IBGP-learned routes are reflected. BGP automatically
>>prevents the set clause of outgoing route maps from affecting
>>routes reflected to IBGP peers. Another automatic restriction
>>concerns the neighbor next-hop-self router configuration command.
>>Because the next hop of reflected routes should not be changed, the
>>neighbor next-hop-self command only affects the next hop of
>>EBGP-learned routes when used with route reflectors.
>>=============================================================================
Cluster-ID should protect against many kinds of loops.
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