North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: honoring AS-path prepend from a peer or customer?

  • From: Avi Freedman
  • Date: Thu Feb 18 21:10:51 1999

In article <[email protected]> you wrote:

: If a peer (or transit customer) prepends their own AS to
: their route announcements to you, do you ever strip off
: the excessive As'es? That is, do you always honor them
: in your announcements to your other customers (or peers)?

: I do understand that any operator has full control over
: deciding his own outbound policy, regardless of the
: AS path.

: I want to know what the industry practice is and whether
: I should stipulate in my next upstream agreement that
: they honor my prepends?

: Thanks.

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...)

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).