unicast reverse path forwarding (unicast rpf), also known as "reverse route lookup," provides inbound and outbound filtering to help prevent ip spoofing. this feature checks inbound packets for ip source address integrity, and verifies that packets destined for hosts outside the managed domain have ip source addresses verifiable by routes in the enforcing entities local routing table.

    unicast rpf is limited to addresses for networks in the enforcing entities local routing table. if the incoming packet does not have a source address represented by a route, it is impossible to know whether the packet arrived on the best possible path back to its origin.