communities are a nice way to add an additional attribute to a route,
independant of the "routing" attributes if you like - I like to think of it
as "colouring" a route.
what I have done in the past is use different communities for different
types of route - I map communities to different "types" of route - for
example, routes learned from:
* downstream transit customers
* upstream transit providers
* per-geographical location
* per-"preferance" - for instance if you multi-home a customer and wish to
have a "customer-preferred" route and a "customer-backup" route
the nice thing is that you can create internal policies based on the source
or type of route - for instance if you multi-home to two transit providers,
you can route-map a local-preference to each provider's routes, and that
will propagate thru you iBGP network without having to mess with AS_PATHs or
prefixes, etc.
hope that makes sense
check out:
http://www.as3257.net/html/communities.htm
for an example of how communites are implemented in the real world - some
sample Cisco comfigs also
Andy
----- Original Message -----
From: "Erich Kuehn"
To:
Sent: Sunday, April 29, 2001 11:20 PM
Subject: BGP Communities [7:2486]
> Can some please explain BGP communities, Ive read through Halabi's =
> description of it and still dont quite understand it's use in a =
> production environment.
>
> TIA
>
> Erich Kuehn
>
> Please no flames, I know this may be a bit basic but, Im just trying to =
> understand this.
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