Avi Freedman freedman at
Fri Aug 2 15:32:39 UTC 1996

> The biggest problem with using non-routable ip addresses on numbered interfaces
> whether point to point or frame or atm or whatever, is that you lose outside
> connectivity from those interfaces.  We tried this, but the essential
> traceroutes from our core routes are too important when debugging BGP 
> problems to the outside.
> Robert Bowman
> Exodus Communications Inc.

Exactly.  Especially when you have downstream customers who only announce
routes via BGP to you and/or other providers, it can be important for them
to be able to trace out with a source address that has global connectivity.

We usually use unnumbered interfaces, though, for singly-connected customers
(unless their routers can't support unnumbered interfaces).  The only
major gotcha with that is that if they're using a Real Router (that deleted
routes associated with interfaces that aren't available), you can't
get to their router if their ethernet is down...


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