PPTP VPN Issues with G3100 Router

I am trying to connect to my work VPN through our new G3100 router that Verizon sent us to replace our old Quantum router. The new router is fine, aside from consistently dropping internet on my work laptop as soon as I try to connect to the VPN. This issue never occurred with the old Quantum router on the same exact service, or any other router I've ever used before, Verizon or otherwise. I am the only person at my company experiencing issues with the VPN, and I can still connect at other locations or with the old Quantum router without any problems. I have attempted split-tunneling, which makes it appear to be connected and it still has internet, but I still can't access my office's network drive, which is the whole point of the VPN.

I think what I need to do is enable port forwarding for TCP 1723 and GRE since this is a PPTP connection (according to our IT guys), but I can't figure out a way to enable GRE in this router's interface.

Both my company's IT and Verizon tech support have been essentially useless in helping me figure this out. Any advice on how to do this, or something else to try, would be greatly appreciated. Thanks!

Accepted answers

smith6612

When running Wireshark, filter down the capture to only your VPN traffic. If the VPN only has one IP address it could be connected to, filter by that IP. Then make sure you're capturing on the network interface supplying your data connection (Ethernet, WiFi) and not the VPN tunnel. Start your Capture, Connect the VPN then try to connect to something. Stop your capture once you feel you've demonstrated the problem.

Uploading a copy of the pcapng file somewhere and DMing it to one of us to look at will help out as well.

Some considerations with VPNs, especially PPTP VPNs. Make sure your VPN client, or computer, has the correct forwarding data in the computer's routing table. If forwarding rules are incorrect and tailored to your old router, that would cause a failure. A lot of PPTP VPNs require manual configuration. Second, make sure the gateway IP and subnet for your G3100 router network does not match that of the VPN, or you're not going to be able to route.

All comments

Cang_Household

GRE is a layer 3 protocol, same level as TCP so you cannot port forward a specific port for GRE.

You need to configure the G3100 for port triggering (not just port forwarding). The incoming port is TCP 1723 then triggers the router to open GRE protocol.

MyCabbages

Ok, that makes sense, thank you!

To be clear, will I still need to set up a port forwarding rule in addition to this, or will this take care of it on its own?

Cang_Household

Outgoing Trigger Ports should take care of the port forwarding.

MyCabbages

Unfortunately, after putting in the port trigger and rebooting the router, I still get kicked off of the internet as soon as I try to connect to the VPN. I have confirmed that the VPN is in fact PPTP by connecting to it from another location and checking in network settings, so I'm surprised it still isn't working. Any other ideas would be much appreciated.

BobAtVdm

Both port 1723 and GRE need to be forwarded, however that can’t be done at the Port Forwarding option. But a new protocol can be created, that includes both port 1723 and GRE. This can be done at the Port Forwarding Rules option under the Advanced section.

From the Home screen, click-on Advanced and Port Forwarding Rules

From the Port Forwarding Rules screen do the following:

Click-on Add.

Enter a name and description. I used VPN and PPTP (it doesn’t matter what you use)

Click-on Add server ports and select

Protocol: TCP

Source Ports: Any

Destination Ports: Single

Enter: 1723

Click-on Add

Click-on Add server ports again and select

Protocol: GRE

Click-on Add

Click-on Apply

We are done at the Port Forwarding Rules screen

From the Home screen, Click-on Firewall, and Port Forwarding

From the “Select IP from menu” drop-down, select IP address you want to forward to

From the “Application To Forward” drop-down, select VPN (or what ever name you used)

Click-on Add

Click-on Apply

We are done.

Cang_Household

Thank you BobAtVdm for sharing the configuration. Are you hosting a VPN server? I think these port forwarding rules are necessary when you are hosting VPN servers.

Does this work when you have multiple clients connecting to different sessions or different VPN servers?