Re: impossible circuit

working, and keeps the dupes from coming back at us, because the ppp encapsulated packets aren't understood by Sprint's routers running [I assume] hdlc...so they can't forward the packets.

AFAIK, routers don't just forward IP packets because they "see" them. That destination MAC address needs to be set to something assigned to the router doesn't it? Unless somehow they've crossed you into some sprint router running IRB? That might be the only exception I can think of.