SoftEther VPN User Forum

This is a general tech query. There’s no problem per say.
In order to connect to my SoftEther VPN server using Windows 10 built-in client using L2TP with preshared key, I need to open ports UDP 500 & 4500 in my router.
It’s working fine; however I am under an impression that the L2TP service runs on 1701 port, but the softether server is configured to run on default
TCP ports like 5555, 1194, 443 etc. I have not modified it at all.
In that case how is the connection actually working? Do services or whatever that runs on UDP 400 & 4500 automatically redirecting the incoming connection to TCP IP 5555?
Thanks.

First IPSec starts on UDP 500/4500 to establish a secure channel and then a L2TP TCP port is negotiated and selected via the channel, which is not 1701 on SE. Elsewhere if IPSec is disabled then L2TP TCP port 1701 is required.