Win7 cannot establish IPv6 L2TP tunnel to SoftEther Server

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Joined: Mon Apr 29, 2024 6:20 am

Win7 cannot establish IPv6 L2TP tunnel to SoftEther Server

Post by wangqiaoqian » Mon Apr 29, 2024 11:07 am

Hello,I use windows7 (by adding a native L2TP VPN) to try establishing IPv6 L2TP connection to the SoftEther server on Centos7, but always failed with "Error 1168:Element not found ....".


(1) the same windows7 can establish L2TP connection by adding a native L2TP VPN with the same L2TP server using IPv4 address without any problem.
(2) the same windows7 can use SoftEther client to connect to SoftEther server using IPv6/IPv4 address without any problem.
(3) windows11 and windows10 can connect to the same IPv6 L2TP server by adding a native L2TP VPN without any problem.

Has anyone encountered this issue, and maybe I missed some configuration or are there some workaround to fix that? Thank you very much in advance.

The configuration for Windows is as follows:
(1) VPN type: L2TP/IPSec
(2) Requires encryption (will disconnect if server declines)
(3)CHAP and MS-CHAP v2 are checked
(4)The correct pre-shared key is entered
(5)The correct username and password are set.

There is no firewall between the IPv6 L2TP/IPSec server and the Windows PC; the server is listening on the ports:
TCP 443
UDP 500
UDP 1701

I have made the following attempts on Windows 7:
(1)Execute ‘sfc /scannow’ with administrator privileges, output no error:
“Verification 100% complete.”
(2)The online solution using the DISM command doesn't apply ,because Windows 7 does not support DISM.
(3)Add key ‘AssumeUDPEncapsulationContextOnSendRule’,value = 2
(4)I referred to the method in this link, but there is no ProhibitIpSec in my registry: ... ows7#p6478
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