consistent policy != consistent announcements

Jessica_Yu · March 14, 1997, 5:48pm

If a provider/AS does not have the policy of dumping hot potatos to other
peers for the traffic to its customers who happen to multihome to those peers.
Then there is a simple way to do it. They can have policy of always favor
its own customer routes over the routes learned from other peers. This will
avoid the inconsistent announcement by eliminating the cases that some part
of the AS favors routes M from it's customer and other part favors M from
another peer, thus announce consistent routes to other peers.

It's very easy to manage this policy. Just assign lower (less favored)
local_pref to routes learned from peers than those learned from customers.
It's AS based. By using the default local_pref value, one only need to
assign a lower than default local_pref value to the peer AS at border routers.

A good side effect of this policy is that your customers routes will be
protected from being blackingholed from careless ISPs leaking/advertising your
customers routes but have no way to reach them.
--Jessica

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References: Your message of Thu, 13 Mar 1997 10:46:06 -0500 (EST)
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