honoring AS-path prepend from a peer or customer?

Jared Mauch jared at puck.nether.net
Fri Feb 19 03:21:03 UTC 1999

On Thu, Feb 18, 1999 at 08:53:09PM -0500, Avi Freedman wrote:
> Standard practice is to accept them, though you may need to tell
> the peer or upstream what regexps to allow if they filter by as-path
> as well as by prefix.  (Always a good idea...)

	Yes, whenever I've set up customer/peer bgp sessions, I've
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.

> My side question is - what shipping routers will let you rewrite
> AS-Paths by doing anything other than just prepending?  Just wondering
> if any 7007-type horrors are lurking in the wings.  I believe Criscos,
> Bays, and gated boxes can't do this (without BGP->IGP->BGP redistribution).

	I'm also interested.  There have been vendor bugs that have tipped
off 7007, etc.. but I'm only really familar with one vendor that (might) be
able to do something like this.

	I would suspect that anyone not honoring your as-path prepending
would be doing as-path filtering.

	- Jared

Jared Mauch  | pgp key available via finger from jared at puck.nether.net
clue++;      | http://puck.nether.net/~jared/  My statements are only mine.

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