[c-nsp] propagate learned MED to peers?

Rainer Clasen bj at zuto.de
Thu Oct 14 15:12:28 EDT 2004


ususally cisco does not propagate the MED learned from other peers to a
different AS. Well, usually this is fine.

Consider an AS with several Confeds. Each Confed originates it's own set
of routes. Each Confed has it's own IGP. All Confeds peer with the same
upstream provider. To save capacity in your own backbone, you want the
upstream provider to send the traffic preferrably directly to the
Confed, where the prefix originates.

In a non-Confed scenario I'd use metric-type internal for setting the
MED. As you have no continuos IGP throughout the Confeds, you can't use

My idea was to increase the MED on each confed boundary and announce
this calculated MED to the upstream provider. Of course you have to be
quite careful with MEDs you receive from peers. Unfortunatly Cisco nukes
the MED, before it is announced.

Well, I can set the MED manually based on communities, as-path or
friends, but this is a hassle to maintain.

Is there a way to announce the learned MED to external peers? Is there
another way to accomplish this?


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