The PPP link control protocol was terminated

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ibghs
Posts: 1
Joined: Tue Dec 29, 2020 3:22 pm

The PPP link control protocol was terminated

Post by ibghs » Tue Dec 29, 2020 3:52 pm

I have set up windows 10 machine with softether VPN server connected to VPN Azure. See https://www.vpnazure.net/en/
I am using other PCs to connect using windows 10 inbuilt VPN client using SSTP.
The connection fails with "The PPP link control protocol was terminated" unless I modify the propoerties of the VPN adapter to allow unencrypted password (PAP).
According to the SSTP Server Function Specifications on SoftEther VPN Server, it should also use MS-CHAPv2 for authentication. See https://www.softether.org/3-spec
But using MS-CHAPv2 fails to connect from multiple machines.

The server spec also states: Compatible VPN Clients: Built-in VPN Clients on Windows Vista, 7, 8, RT
I am using Windows 10.

1. Is MS-CHAPv2 authentication with SoftEther SSTP Server incompatible with Windows 10 client or server?
2. Is PAP unsafe or is there any layer of encryption around the password transmission using the Windows 10 VPN client?
3. Please advise what else to try on either the SoftEther VPN or Microsoft VPN client.

Thank you
IanB

ZEE
Posts: 7
Joined: Wed Dec 12, 2018 3:47 pm
Location: Fafe, Portugal

Re: The PPP link control protocol was terminated

Post by ZEE » Thu Feb 10, 2022 2:15 pm

Same problem here,,, ?any luck...

eddiewu
Posts: 286
Joined: Wed Nov 25, 2020 9:10 am

Re: The PPP link control protocol was terminated

Post by eddiewu » Thu Feb 10, 2022 3:01 pm

Using PAP solves the problem. Have you tried?

myron.s
Posts: 7
Joined: Sun Nov 29, 2020 4:38 pm

Re: The PPP link control protocol was terminated

Post by myron.s » Thu Feb 10, 2022 3:35 pm

Was the SoftEther server's certificate installed in the Windows 10 Trusted Root Certificate Authorities store? There are two things at work here. First a secure connection is established between the VPN server and the Windows 10 client, authenticated by the certificate provided and imported from the SoftEther VPN server and then there is the username and password.

I'm using MS-CHAPv2 without any problems.

PAP should be ok because of the secure socket tunnel created between Windows 10 and the SoftEther server so the unencrypted password would be transmitted through the secure socket tunnel.

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