Gabi, Correct me if I am wrong, but if there were a new version of ISATAP that did not use ip-proto-41 encapsulation but instead used a different kind of encapsulation, then it need not concern itself with routing loop interactions with 6to4 relays since 6to4 relays only know about ip-proto-41. Does that match your understanding? Thanks - Fred fred.l.templin@boeing.com