RE: [isp-bgp] filtering pratice

["Darrell Hyde" <DHyde@...>]

> when i discussed this "issue" with a friend of mine, and i suggested
> that we should filter on their community, he told me that 
> communitys are
> _only_ there for engineering, so we can change how our peers are
> treating our routes. I understand how that works, that we can set
> different communities then our peer will treat us different, 
> that's not
> the problem. So, if i understand you right, it's a 
> common/good/whatever
> thing to filter on their communities?

That's correct - BGP communities don't have any inherent effect on the
BGP decision making process, and are not created by any automated
process. They are used to manually group and identify routes and when
exported to peers, can be used to easily identify routes in a route-map
or other filtering mechanism. 

It's a fairly common practice for an ISP to support both communities to
identify their "on-net" routes, and to support to export of several
communities to them for purposes of adjusting local pref of your routes
on their network. This information is commonly available on an ISP's NOC
page or can be provided by contacting their support group. 

A good example is Sprint who clearly lays all of their BGP policy info
here: http://www.sprintlink.net/policy/index.html

- Darrell





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