nanog mailing list archives
Re: What's the point of prepend communities?
From: Leo Bicknell <bicknell () ufp org>
Date: Thu, 26 Oct 2017 12:19:43 -0700
In a message written on Thu, Oct 26, 2017 at 02:47:44PM -0400, Jason Lixfeld wrote:
I understand how prepends fit in the context of best path selection, but my question was more the difference between a customer signalling the ISP to prepend their AS using a BGP community stamped to a prefix vs. the customer prepending their own AS instead.
Imagine: You are 1. ISP is 2. ISP's peers are 3 & 4. Your B2B partner is 5. There are paths: 1 2 3 5 1 2 4 5 If you prepend your ASN, you get: 1 1 2 3 5 1 1 2 4 5 No difference. If you send the ISP a prepend community for 3, you get: 1 2 3 3 5 1 2 4 5 And you just forced all traffic to the second, shorter path. -- Leo Bicknell - bicknell () ufp org PGP keys at http://www.ufp.org/~bicknell/
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Current thread:
- Re: What's the point of prepend communities?, (continued)
- Re: What's the point of prepend communities? Jason Lixfeld (Oct 26)
- Re: What's the point of prepend communities? Christopher Morrow (Oct 26)
- Re: What's the point of prepend communities? Job Snijders (Oct 26)
- Re: What's the point of prepend communities? Jason Lixfeld (Oct 26)
- Re: What's the point of prepend communities? Rob Foehl (Oct 28)
- Re: What's the point of prepend communities? Jason Lixfeld (Oct 26)
- Re: What's the point of prepend communities? William Herrin (Oct 26)
- Re: What's the point of prepend communities? William Herrin (Oct 26)
- RE: What's the point of prepend communities? Naslund, Steve (Oct 26)
- Re: What's the point of prepend communities? Brett Frankenberger (Oct 26)
- Re: What's the point of prepend communities? Steve Dodd (Oct 28)
- Re: What's the point of prepend communities? Leo Bicknell (Oct 26)
- Re: What's the point of prepend communities? Clinton Work (Oct 26)
- RE: What's the point of prepend communities? Naslund, Steve (Oct 26)
- Re: What's the point of prepend communities? Leo Bicknell (Oct 30)
- Re: What's the point of prepend communities? Michael Hallgren (Oct 30)
- Re: What's the point of prepend communities? Mike Hammett (Oct 29)
- Re: What's the point of prepend communities? Brett Frankenberger (Oct 29)