I'm using NAT overload on a 857 router and have ip nat static entries for port forwarding smtp, http etc. which are all working fine.

Problem lies in vpn connection to windows pptp server. I've used ip nat static source tcp 192.168.x.x 1723 interface dialer0 1723 command to pass vpn to windows box which seems to working fine because I can connect, authenticate and then ping devices on the network. But if i try to use say rdp or vnc to connect to a pc on the network it, normally, just hangs. VNC for example asks for the connection password then when the screen should appear the connection hangs. Actually I've discovered that sometimes VNC will work but only for a few mins then it loses connection and I can't ping or anything.

Also noticed that if I stay connected for a few mins even pings stop working and I have to disconnect and re-connect.

Any ideas?

oh and I get icmperr entries in show ip nat translations - don't know if that's related?