[23088] in North American Network Operators' Group
Re: honoring AS-path prepend from a peer or customer?
daemon@ATHENA.MIT.EDU (Avi Freedman)
Thu Feb 18 22:49:34 1999
From: Avi Freedman <freedman@avi.netaxs.com>
To: jared@puck.nether.net (Jared Mauch)
Date: Thu, 18 Feb 1999 22:33:09 -0500 (EST)
Cc: nanog@merit.edu
In-Reply-To: <19990218222103.A10672@puck.nether.net> from "Jared Mauch" at Feb 18, 99 10:21:03 pm
> done it such that we only did prefix filtering, not any as-path
> filtering, this allows them to prepend as they wish, just not advert
> anything other than what we filtered them at.
FYI, this is dangerous.
For example -
You have a customer A who has a customer B.
B is multi-homed to A and 701.
B's link to A goes down.
So, if A's network is broken, they will send you a given prefix
with as-path ^701 B$ or ^1239 701 B$ or ..., depending on how B
sees 701.
And you will transit it.
Shouldn't cause any major damage, but something to be aware of.
> - Jared
Avi
