And just to update, those drafts have made it into RFC 4271 http://www.ietf.org/rfc/rfc4271.txt -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Danny McPherson Sent: Tuesday, January 03, 2006 3:49 PM To: nanog@nanog.org Subject: Re: metric 0 vs 'no metric at all' On Jan 3, 2006, at 1:03 AM, Daniel Roesen wrote:
So the spec is fuzzy about how "no MED vs. MED=0" should be treated, but vendors seem to largely agree to "no MED == MED 0". I know of no deviation, except the old ERX bug which got fixed (ERX treated "no MED" as best, even better than MED=0 - contrary to documentation).
I recall some earlier implementations from "well known" vendors that had varying behavior for MED processing as well. Fortunately, the update to RFC 1771: http://www.ietf.org/internet-drafts/draft-ietf-idr-bgp4-26.txt is considerably more explicit about this behavior, as well as a slew of other previously-left-to-the-implementation items ironed out through a great deal of implementation and deployment experience. The "BGP Experience" and "BGP MED Considerations" Internet- drafts provide a good bit of additional insight into some of these behaviors. -danny