From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Tue Mar 13 2007 - 15:10:41 ART
By default all community values (standard and extended) are
stripped from BGP advertisements when sent to iBGP or EBGP neighbors.
If you want to propagate community values on you must use the
send-community option at the end of the neighbor statement.
The issue you're running into is dependent on whether you have
the community set locally or you are setting the community value
outbound to the neighbor. If you receive a prefix with the community
no-advertise you don't necessarily need the "send-community" option on
to your neighbors because the prefix is not candidate to be advertised
to the neighbors regardless. If you receive a prefix with a community
of no-export for example you will not advertise it to EBGP neighbors,
but when you advertise it to iBGP neighbors the community attribute will
be stripped unless you add the send-community value at the end of the
neighbor statement.
HTH,
Brian McGahan, CCIE #8593 (R&S/SP)
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
premkumar somasundaram
Sent: Tuesday, March 13, 2007 7:16 AM
To: ccielab@groupstudy.com
Subject: Community List
GS,
I have a doubt about community list in bgp. When do we want use the
neighbour x.x.x.x send -community. When I use the community value,
No-export, I must use the neighbour x.x.x.x send-community. But when I
use
the community value, No-advertise, even when I am not using neighbour
x.x.x.x send-community, it solves the purpose. Is there any logic behind
the
use of send-community or am I going wrong somewhere??
Thanks
prem
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