Our office has a number of incoming PPTP connections to our TP-Link TL-R600VPN router from a number of Windows Embedded for Point of Service (WEPOS) terminals located in our restaurants.
One restaurant location is successfully connecting to our router, however reaching it over the network from the office is proving troublesome. I've attempted to ping the machine whilst its connected to the router but I just get
request timed out errors. This is an isolated case, all of our other terminals respond to ping and I can successfully connect to them via FTP and VNC (which is what we use the VPN for).
I assume therefore that this is a client issue, but I have no idea where to start looking. Can anyone provide some suggestions?
--- Edits in response to Tom --- Our main router (TP-Link TL-R600VPN) has a built in PPTP server with MPPE enabled. I'm unaware if it has GRE or not, but as all the other clients are connecting I assume yes.
All of the client machines are running Windows Embedded for Point of Service (WEPOS) 2009 and connect using the Windows dial-up (rasphone.exe) client. Windows firewall was enabled on the machine, and I have since disabled it for testing along with antivirus.
The router LAN is running on 192.168.7.0 with a subnet mask of 255.255.0.0 - VPN clients are assigned addresses in the 192.168.77.0 subnet. All of our client terminals sit behind NATs themselves (with PPTP pass-through enabled) and run on a 192.168.2.0 LAN subnet, with a subnet mask of 255.255.255.0.
Interestingly in further tests I've discovered that all of the VPN clients on the same subnet can connect to this one terminal without issue. It's only the workstations on the LAN that continuously time out. Running arp -a from any of the LAN based workstations displays the VPN client in question, but I can't get any further than this.