[USR-TC] Help: Dropping packets for not-in-use IPs

I've got a strange thing happening with one of my USR HiperArcs. Someone, somewhere, is trying to DDOS a dialup customer's IP address. This is annoying enough, but that IP isn't even in use right now. So the packets just keep bouncing back and forth around my office. Traceroutes just keep going back'n'forth between the USR and its gateway, each of which thinks the other is the right place for this packet to be. Is there a way to convince the HiperArc that it's the "final" destination for all the addresses in its IP pools, and to drop packets destined for IPs in that pool that aren't connected right now? (If this is too vague, let me know and I'll gladly provide any extra details needed.) Thanks! David Smith MVN.net