And then there is http://www.cisco.com/warp/public/707/newsflash.html. It says that the RPF check is based on CEF. I'm not familiar with CEF and want to clarify something about unicast RPF. If the source address of a packet arrived on an interface that would not be the preferred route for that address but is one of the less-preferred routes would the packet get dropped? Nope it has to be the preferred route. If, as I hope, it would not, I don't understand the argument that it doesn't work for multi-homed connections. Such systems should be advertising their routes over all connections - thus the routes should appear on all paths outbound from the multi-homed systems (less any long prefix filtering being done by the upstreams). I agree it would be more helpful if the test was "a route exists" instead of "the best route" as I have seen it cause havoc with customers who have multiple links to us and get the MEDs wrong. Mark.