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Re: BGP4 COMMUNITY attribute

  • From: Paul G. Donner
  • Date: Thu Mar 27 14:25:27 1997

Actually, along this vein (granted, this may not be the place but since
the subject came up)..

What is the general concensus about passing communities in the "community"?

See in-line below...

At 01:32 PM 3/27/97 EST, John W. Stewart III wrote:
>
>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

Unless an intermediate provider deliberately changes the value, as
opposed to appending to it.

>practice, many providers are configured to not send communities
>to other providers

Is this a conscious decision or just that they have not turned on 
"send-community"?

Donner

>
> > 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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