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List:       isp-bgp
Subject:    [isp-bgp] RE: Communities Faq/Tutorial/Documentation
From:       "Pete Templin" <pete.templin () texlink ! com>
Date:       2003-12-03 19:04:13
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Think of communities as little sticky notes that you can slap on the back of each \
route.

I use them internally at TexLink to track the source of the route.  All \
Texlink-originated routes are tagged 11457:11457, all routes learned from an upstream \
are tagged 11457:11460, and all routes learned from a downstream customer are tagged \
11457:11456.  I can easily block any upstream routes from passing to another upstream \
by just checking for 11457:11460, and can also easily do tuning based on the \
communities, etc.

I also tell our downstream customers that they can send any more-specific prefix of \
their space with a community of 11457:0, and we will route that subnet to NULL for \
them (if they're under attack, etc.).  Basically, you can write your route maps to \
apply various BGP tunings by matching the community list.  If you creatively apply \
the communities at your borders, you can do all of your filtering throughout your \
network by community, rather than having to write as-path regular expressions or \
prefix lists all over your network.

Pete Templin
Senior Staff Engineer
TexLink Communications
(210) 892-4183
pete.templin@texlink.com


-----Original Message-----
From: Rick Kunkel [mailto:kunkel@w-link.net]
Sent: Wednesday, December 03, 2003 12:12 PM
To: isp-bgp@isp-bgp.com
Subject: [isp-bgp] Communities Faq/Tutorial/Documentation

Is there a good source out there for information on how communities work?
In just about all the material I have, either communities are not
mentioned at all, or else the documentation says something classic, like
"communities are beyond the scope of this book".

Thanks,

Rick Kunkel



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