Apologies for replying to a really old message but... $quoted_author = "Ondrej Zajicek" ;
On Mon, Mar 28, 2011 at 03:25:51PM +0400, Mikhail A. Grishin wrote:
Hi, Ondrej
Thank you for explanation.
One more question: is it possible to add "bgp always-compare-med" option in BIRD?
That would not be a problem. A question is under which circumstances such comparison has some sense. Probably only if user overwrites all MEDs on input to the AS.
Manipulating MED is not common but also not unusual. It tends to be used in situations where manipulating LOCAL_PREF results in too many sub-optimal paths and letting the decision fall through to ROUTER_ID would not achieve the desired effect. e.g. - Two different upstreams - We want to use shortest AS_PATH where possible - But if AS_PATH is same length we want to prefer ISP A - We can't adjust LOCAL_PREF with a prefix filter because it's not a known set - But ROUTER_ID would pick ISP B - Only option is to manipulate MED and use always-compare-med