We have a Comcast Business SMC Networks modem hardware version 1B and are having problems getting PPTP to pass through. I have called Comcast and they say it should work. The only options for port forwarding on this modem are for TCP and UDP. We need the GRE packet forwarded to enable PPTP to reach the server. If we enable DMZ to the server, we can VPN to the server. However, this opens up all ports. We have called in and asked if they can enable PPTP passthrough on their end and they say they cannot. Is there a way to forward the GRE packet on this modem without using DMZ?