L2TP/IPSec VPN Connection without encryption

Question

My ISP provided us with VPN connection that comes with Gateway IP, Username & Password. We connect through windows server 2016 fine with no issues

Screenshot: Configuration of the VPN on windows

Now we want to switch to Ubuntu, but we are having issues connecting with IpSec/Strongswan

as the connection requires PSK or some kind of encryption

How can we connect using only user&pass

Answer 1

On Windows you have configured a L2TP VPN connection without IPsec (i.e., no encryption).

On Ubuntu you can install the network-manager-l2tp and network-manager-l2tp-gnome packages. Don't enable IPsec in the IPsec Settings and in the PPP Settings disable all authentication methods other than CHAP and MSCHAPv2.

It seems crazy any ISP would be offering L2TP without IPsec. In the PPP Settings you could try enabling Use Point-to-Point encryption (MPPE) so that it is using some encryption albeit weak.