BGP4 COMMUNITY attribute

Walter Towbin Walter.Towbin at TELUS.COM
Thu Mar 27 18:24:33 UTC 1997

In the preparation for upcoming 2nd (multihomed) connection to Internet
I am looking into
COMMUNITY attribute of BGP4 as a way (in conjunction with my own
LOCAL_PREF) of load balancing
traffic between my two internet links (both T3). After reading CISCO
documentation I am still not
clear on some issues:

1. Is COMMUNITY a transitive attribute only between me and my immediate
upstream supplier or 
is it being propagated further into Internet (so I can influence how
somebody ,say, 5 AS hops 
away from me sees my routes) ?

2. If COMMUNITY propagates into big I, and I set COMMUNITY to 3561:70
(for MCI to set 
LOCAL_PREF on my routes to 70) and my next hop supplier sets COMMUNITY
of my routes to  
3561:80, what happens ? what MCI is going to do ?

3. Is COMMUNITY a CISCO only or is it part of RFC ? Has any other router
vendor implemented
this parameter ?

4. Which major Internet providers have COMMUNITY/LOCAL_PREF implemented
 (I am aware of MCI and Sprint) ?

5. Your experiences, comments, suggestions .....

Thanks in advance, Walter

Walter Towbin
Telus Advanced Communications
phone: 403-543-2032, fax: 403-543-2030, cell: 403-620-0019
walter.towbin at

More information about the NANOG mailing list