PPTP VPN works fine at first but then stops

I have users connecting from Windows laptops (Win 7 thru Win 10) to the office network using the built-in Microsoft VPN client and standard PPTP connection.

I believe I have all the necessary ports and protocols allowed through the firewall which is a SonicWALL NSA2400.

Then I have Routing and Remote Access set up on a server running Windows Server 2012 Standard.

The VPN works fine for some users. And when I test it, it seems to work fine. But a few users have a weird issue where the VPN will connect normally and they are able to access network resources normally at first and then stops working.

Typically, the user will connect, access a server (\\servername), and begin to browse shared folders. It will work perfectly for maybe the first 3-5 folders they click on but then it will suddenly stop working. Explorer will show the green bar slowly filling the address bar but then nothing else will come up. The VPN connection will still be active and connected and I can still ping servers and do DNS lookups. But shares can no longer be accessed.

Disconnecting the reconnecting the VPN will start the process over where it works for a bit and then stops.

Any ideas what might be happening?
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JohnBusiness Consultant (Owner)Commented:
You have multiple computers with various operating systems connecting to ONE Server.
Then ALL (or most) of the above computers have erratic connections to the Server.

Is this correct?  I think it is what you said.

So it is not likely the operating system because several are involved. It is not likely the computer hardware (like network card) because multiple are allowed.

I would look at:

1. The office router. Upgrade the firmware and/or try a different router.
2. Check firewall settings in the office setup.
3. Remake the VPN setup in Server 2012.
4. Make sure there are no user restrictions about access in AD.
Aaron TomoskyDirector of Solutions ConsultingCommented:
The sonicwall works great as a Vpn server, I would setup l2tp or Sslvpn or the globalvpn client on the sonicwall instead of passing the ports through to windows.

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MosaicRPAuthor Commented:
@John – thanks for the reply. I believe we have the latest firmware in our SonicWALL. And I have tried fully disabling the Windows firewall on the client computer but no change. I don’t believe there are any restrictions in AD. What is odd is that I would think this would be an “all or nothing” type of thing. It really strange that it works at first and then stops and that it is only affecting some users.

@aaron – thanks for your reply as well. We do use the SonicWALL as a VPN server as well with the global vpn client. But we only have 10 licenses of that. You mentioned L2TP. Can we use that without licensing?
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JohnBusiness Consultant (Owner)Commented:
Since you have all different computers, it has to be an office setup issue.

Make sure your licensing is up to date - you did not mention how many users. 1 user of 10 could not connect, then connect later, then different user cannot connect.

Make sure you have enough CAL's for your server because that could cause the same issue.
Aaron TomoskyDirector of Solutions ConsultingCommented:
I believe l2tp uses global vpn licenses. SSL VPN licenses are separate. They are both concurrent licenses, not per user if that helps. Also it's not expensive to add more.
MosaicRPAuthor Commented:
This turned out to be the easiest solution. The global client works well and the additional licenses are not that expensive. Thanks for the help.
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