From: Chua, Parry (Parry.Chua@xxxxxxxxxx)
Date: Thu Nov 22 2001 - 00:53:26 GMT-3
This is what I think it work, if you configure RR is the centre of the
Ibgp cloud,
then any community set from client will pass to the RR, we should have
instruct the
RR to have the neigh x.x.x.x send community to the client which we want
the community to pass to that client. otherwise, it just like a full
mesh Ibgp peers and with the route-map on set community w/o passing the
send community to the client.
Parry Chua
-----Original Message-----
From: Robinson [mailto:kensue@easystreet.com]
Sent: Thursday, November 22, 2001 9:17 AM
To: ccielab@groupstudy.com
Subject: BGP Community Attr. and Route Reflectors
Ive been going through Hutnik & Satterlees All-in-One Cisco CCIE Lab
study guide 2nd Ed. (Good book BTW), and developed the following
question that doesnt seem to be answered by that book, nor by Halabis
Internet Routing Architectures, nor by other books Ive looked in. Im
hoping that this list will be more informative.
When configured and applied, the well-known BGP community attribute
NO_EXPORT should prevent a BGP route advertisement to routers outside
the local AS (H&S pg.584 and Halabi pg.165).
Okay so far, but in the example given in H&S on pg. 591 the authors
indicate that this community attribute will not be passed to other IBGP
routers without a fully meshed topology (see excerpt below). This in
spite of the fact that route reflectors have been set up.
Doesnt this therefore reinstate the requirements for a fully meshed
IBGP topology (i.e.- lots of neighbor statements), negating the utility
of route reflectors? Granted, the answer may be to avoid use of
community attributes, but I suspect theres something Im missing.
I would welcome any thoughts, comments, winning lottery tickets, etc.
from the list. Thanks in advance for your help!
-Ken
Excerpt from Hutnik & Satterlees All-in-One Cisco CCIE Lab study guide
2nd Ed., pg. 591:
The reason that RouterC is still advertising the network [in spite of
the NO_EXPORT attribute] is that the community attribute was not passed
by RouterB [configured as route reflector]. The send community option in
the neighbor router subcommand is needed to cause the community to be
sent to the BGP neighbors.
RouterB(config-router)#neighbor 152.1.2.1 send-community
[Bracketed text added by me]
Ken Robinson
Senior Network Engineer
Oregon Networks Consulting
krobinson@oregonnetworks.com
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