If you have a Linksys BEFSR41 router and connect to a VPN (Virtual Private Network) server sitting behind it, DO NOT upgrade the firmware to the latest 1.45.6 version of the firmware as the PPTP pass through is well broken in this version. Stick to the 1.44.2 version. It might just save you all the trouble having to set up a network sniffer to see if IP 47 GRE packets are passing through the router. Especially if it happen to be on a Friday evening that is on the eve of a long weekend.