consistent policy != consistent announcements

Vince Fuller vaf at
Thu Mar 13 19:42:25 UTC 1997

    add a peer P to your first example.  if P peers with you at
    Point1 close to A's connection and again at a Point2 close
    to B's connection, then P will hear M's prefixes at Point1
    as "R A M" and at Point2 as "R B M".  but because the AS
    path length is equal, they'll still be able to do closest
    exit for M's prefixes.

If that were happening, then we'd consisder the routes to be consistant, at
least for shortest-exit purposes.

What we are seeing, though, is "R A M" at Point1 and nothing at Point2, likely
because Randy doesn't consider "R B M", received from one of his peers, to be
a customer route.

    the tone of the "consistent route" policy is to keep one provider from
    having to carry packets cross-country in both directions:

Full agreement.

    in this example P does not have to do that

In your example, you are correct. But your example doesn't match the situation
that Randy is describing.


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