Re: BGP4 COMMUNITY attribute

["John W. Stewart III" <jstewart () isi edu>]

many of your questions are for MCI and not nanog

> 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) ?

the attribute is defined as transitive (i.e., once associated
with a route it *stays* associated with the route).  however, in
practice, many providers are configured to not send communities
to other providers

> 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 ?

is one of your immediate upstream provider's MCI?  if so, then
you would tag routes with 3561:70 and MCI would immediately see
and react to that.  however, you imply that your "next hop
supplier" isn't MCI, which makes it a bit odd for you to be
sending communities for MCI, but is doable if your "next hop
supplier" agrees to carry your communities all the way to MCI

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

rfc1997.  i think there's a GateD with communities

/jws

> 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 () telus com
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