I have set up a brand new Draytek 2952 with the latest firmware 3.9.0. I have an external RADIUS set up so that it should authenticate domain users using the external radius server (setup on Windows server on the same network).

When trying to connect Host to LAN over L2TP with PSK using the built-in Windows 10 VPN functionality, it says "Connecting" for a second, then "Verifying your sign-in info" for about 15 seconds and finally errors with

Can't connect to [VPN Name]. The connection was terminated by the remote computer before it could be completed.

Looking at the Windows logs, there aren't any errors from the RasClient and the final informational message says:

CoId={[GUID]}: The link to the Remote Access Server has been established by user [Username].

Looking at the RADIUS server logs, is it successfully getting a request from the Draytek firewall and is allowing the user access based on the network policies I have set so I don't think the issue is here.

"[DC]","IAS",02/28/2019,14:45:32,1,"[User]","[User Location]",,,,,,"[Draytek IP]",,0,"[Draytek IP]","Firewall (Draytek)",,,,,1,2,4,"UK Draytek Firewall",0,"311 1 [RADIUS IP] 02/27/2019 14:53:48 482",,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,"Use Windows authentication for all users",1,,,,

"[DC]","IAS",02/28/2019,14:45:32,2,,"[User Location]",,,,,,,,0,"[Draytek IP]","Firewall (Draytek)",,,,,1,2,4,"UK Draytek Firewall",0,"311 1 [RADIUS IP] 02/27/2019 14:53:48 482",,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,"0x00464954",,,"Use Windows authentication for all users",1,,,,

I have the exact same model firewall in a different physical location connecting to the same network via LAN to LAN, with the same setup, pointing to the same RADIUS server and it works fine. The only two differences I can see are:

  1. The one which doesn't work is on a newer firmware version. The working one is on and the non-working one is on 3.9.0. I'm thinking this could be an issue with the latest firmware?
  2. The one which isn't working is behind a NAT-T device whereas the working one isn't. I had to complete these steps to get it connecting in the first place https://support.microsoft.com/en-gb/help/926179/how-to-configure-an-l2tp-ipsec-server-behind-a-nat-t-device-in-windows

Another quirk is this was 100% working one night when it was set up, continued working the next day and then around midday, stopped working and nothing had changed in the config, which makes me think it is firmware related?

If there's any other information anyone needs to help, please let me know. Help would be greatly appreciated!

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