Why does windows10 connect to the router via L2TP / ipsec normally, and to ubuntu - only with a registry patch?

Question

linux

The router has a configured L2TP / ipsec server with a shared key - windows 10 connects to it without question.
There was a task to lift the L2TP/ipsec server on Linux.

According to this article, I did it (like even fresh) on a virtual machine in the local network.
https://interface31.ru/tech_it/2021/06/nastraivaem...

But windows 10 doesn't want to connect to it without this registry edit:
[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Rasman\Parameters]
"ProhibitIpSec"=dword: 00000001

This error is in the logs:
CoID={C51F1124-0DE6-0000-353D-1FC5E60DD801}: The SYSTEM user has established a remote connection test, which has failed. Error code 789 returned

. What does she want?

Answer 1

Or you don’t have ipsec configured correctly or you are affected by a problem with windows updates, you may be connecting to the router without encryption.
https://habr.com/ru/news/t/645131/