I have a L2TP/IPsec server setup on a CentOS box that I am using for multiple purposes, and I wish some clients connect one way, other clients connect the other way, and get different sets of resources. I have decided that the best way here would be to set up two different xl2tpd instances, one to use Windows domain authentication listening on port 1701, another to use file-based auth (local logins) and use port 1702. I have tried to test these VPN connections from a Windows box located elsewhere, and have found out that with Windows' VPN client I can only set up the type of VPN (along with auth factors etc) but not server port when it comes to L2TP/IPsec connections. Is there any way to specify a port to L2TP/IPsec connection for Windows?
PS: tried adding a port to IP, received "cannot resolve", as the VP{N client apparently is not expecting a pair of IP:port in the connection string.
Unfortunately, Windows VPN Client is not capable of changing the target TCP port of VPN connection.
I would recommend you to setup a second IP address on your CentOS box and assign different xl2tpd instances to different IP addresses instead of ports. This way you can configure your Windows-based clients to connect to one or another VPN server IP address depending on authentication type required.