AS path question.

Stefan Fouant sfouant at shortestpathfirst.net
Wed Nov 10 15:35:41 CST 2010


BGP community attributes are optional transitive attributes, so in theory they could be used by secondary or tertiary providers for policy processing.  However, that is under the assumption that those providers have the proper policies in place and understand those communities.  Alsi, in some cases a given provider will strip the communities out before advertisement to upstreams or upon receipt from a downstream, so there is no guarantee that the communities will remain intact.

Typically however, the community tagging is used to influence the direct upstream providers, and the AS Path prepending is used to influence the secondary providers.

Stefan Fouant  

My apologies for the top post.  Sent from my iPad

On Nov 10, 2010, at 4:12 PM, Joe Maimon <jmaimon at ttec.com> wrote:

> 
> 
> Stefan Fouant wrote:
>>> -----Original Message-----
> 
>> 
>> IMO, a combination of both community tagging to influence localpref coupled
>> with AS Path prepending on the secondary link is the best approach, and
>> seems to accommodate both steady state as well as failure scenarios
>> properly.
>> 
>> Stefan Fouant
> 
> 
> So how far from you can you propagate community tags to influence the route decision process to your second transit upstream peer?
> 
> 
> Joe




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