On 8/Jan/20 16:52, James Jun wrote:
I see. LOCAL_PREF and RFC 1998 style of community attributes however are not the right tool for signalling exit locations -- it does not scale. Sure, it's a useful hammer to hard enforce a baseline mode of preference on given route (e.g. route of last resort, backup or equalize to same baseline level as peer-learned routes, etc), but for signalling optimal exit locations at scale, MED is exactly the right tool for that job (and networks would typically derive MED values using IGP metrics).
Two solutions, two methods, same result, IMHO. It's been scaling very well for us, and offers customers explicit control that comes with a flip-switch cover over the, well, switch :-). If you know of any reason why LOCAL_PREF doesn't scale, I'd like to hear it, since I'd imagine that if closely maintaining exit paths is important to you, you don't want to leave it to chance anyway. Mark.