L2tp / IPSEC is very specific about requiring the server ports to be UDP 500, 1701 and 4500, and ESP protocol 50, although when using NAT transversal the ESP packets get sent over UDP. A CGNAT at your server ISP may mangle these ports, and that could happen to port 4500 intermittently.
External links Implementations. Cisco: Cisco L2TP documentation, also read Technology brief from Cisco Open source and Linux: xl2tpd, Linux RP-L2TP, OpenL2TP, l2tpns, l2tpd (inactive), Linux L2TP/IPsec server, FreeBSD multi-link PPP daemon, OpenBSD npppd(8), ACCEL-PPP - PPTP/L2TP/PPPoE server for Linux Microsoft: built-in client included with Windows 2000 and higher; Microsoft L2TP/IPsec VPN vpn-client · GitHub Topics · GitHub Jul 12, 2020 What is IPsec VPN encryption? | 5 best IPsec VPN clients Jul 02, 2020
Sep 16, 2012
And I have read somewhere that it can’t be used fo L2TP and IPSec. I would very much appreciate if someone can help me set up this vpn, because the other option is to switch OS… windows, maybe other linux… don’t want to think about it, I have everything set up here and I don’t want to change OS just for a vpn. Layer 2 Tunneling Protocol - Wikipedia External links Implementations. Cisco: Cisco L2TP documentation, also read Technology brief from Cisco Open source and Linux: xl2tpd, Linux RP-L2TP, OpenL2TP, l2tpns, l2tpd (inactive), Linux L2TP/IPsec server, FreeBSD multi-link PPP daemon, OpenBSD npppd(8), ACCEL-PPP - PPTP/L2TP/PPPoE server for Linux Microsoft: built-in client included with Windows 2000 and higher; Microsoft L2TP/IPsec VPN vpn-client · GitHub Topics · GitHub
SoftEther VPN - Wikipedia
Using a Linux server with the Microsoft L2TP/IPSec VPN Client