From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Thu Apr 29 2004 - 08:09:36 GMT-3
At 8:03 PM -0700 4/28/04, Yinglam Cheung wrote:
>Yes, Cisco changed the default bgp behavior from synchronization to
>"no sync" one or two years ago. I noticed that after upgrading a GSR
>with an IOS version in ST train.
>
>I believe Cisco has done this quietly on other IOS trains. :)
The key question is whether they've taken it out of exams!
Given the constant pressure to fit in new topics, it would be
reasonable to do so. Unfortunately, I suspect there is sometimes a
regenerative feedback mechanisms in Cisco -- it certainly was true in
courseware -- that if lots of people were getting something wrong,
more and more would be said about it.
>
>"Howard C. Berkowitz" <hcb@gettcomm.com> wrote:
>At 9:39 AM -0700 4/28/04, Edwards, Andrew M wrote:
>>I'm trying to understand methods to keep synchronization on in BGP and
>>provide BGP to OSPF redistribution with route reflectors.
>
>Perhaps someone can confirm this, but I seem to remember that Cisco
>finally admitted synchronization is a completely obsolete technique
>and has taken it out of the exams. The general idea of
>synchronization, in part, comes from RFC 1403, which has been put in
>"HISTORIC" statues -- i.e., obsolete -- by the IETF.
>
>So, we have the problem, which may not be fully understood especially
>by some review materials, that things like route reflectors were
>never intended to work with synchronization, and developing practice
>examples to do this is fundamentally futile. "synchronization has
>been assimilated..." :-)
>
>>
>>You know the problem where the route reflector server receives an update
>>from a route reflector client that is redistributing BGP to OSPF.
>>
>>When the route reflector server gets the update, it reflects that update
>>to all other RR clients but changes the BGP ID to itself.
>>
>>Obviously the other BGP RR clients get the BGP update but the OSPF
>>router ID and BGP ID do not match on the clients so the BGP route is not
>>marked
>>As a best path ">"
>>
>>So the question I have is what methods are available to make this work
>>with synchronization on and using route reflectors?
>
>See RFC3345 Border Gateway Protocol (BGP) Persistent Route
>Oscillation Condition. D. McPherson, V. Gill, D. Walton, A. Retana.
>August 2002 http://www.isi.edu/in-notes/rfc3345.txt
>
>>
>>Is the answer go to full mesh or transfer to confederations?
>
>The above RFC generally recommends full mesh within a cluster, or
>additional constraints on IGP metric and other things that affect
>preference within the cluster. It's good to read this and compare
>the ideas in it with the reasons OSPF always prefers intra-area
>routes over inter-area over external.
>
>>
>>I'm stumped on how to change the BGP router-id to the originators BGP
>>router ID on the RR server.
>>
>>Thanks for the input... or clearing up my confusion.
>>
>>Andy
>>
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>best regards,
>Yinglam Cheung
>CCIE #6961 (R&S, Service Provider, Security)
>
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