Downstream Usage-BGP Communites

Michael Hallgren m.hallgren at
Tue May 10 22:07:13 UTC 2011

Le mardi 10 mai 2011 à 17:52 -0400, Nick Olsen a écrit :
> Greetings NANOG,
> Was hoping to gain some insight into common practice with using BGP 
> Communities downstream.
> For instance:
> We peer with AS100 (example)
> AS100 peers with TW Telecom (AS4323).
> Since I happen to know that AS100 doesn't sanitize the communities I send 
> with my routes. I can take advantage of TW Telecom's BGP communities for 
> traffic engineering. Such as 4323:666 (Keep in TWTC Backbone). Would this 
> be something that is generally frowned upon? Still under the assumption 
> that the communities aren't scrubbed off my routes. Could I do this with 
> other AS's beyond TW Telecom? Such as TW's peering with Global Crossing 
> (AS3549)?

It's quite common, in my experience, that we remove (or at least filter;
usually looking at geo-origin ones only) BGP community values from peers
and filter them (modulo some set of agreed ones) from customers. 

In other words, don't generally expect transitivity.


> Nick Olsen
> Network Operations (855) FLSPEED  x106

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