L2TP/IPSec

L2TP is an older tunneling protocol that provides no encryption of its own, so it is almost always deployed together with IPsec, written as L2TP/IPsec. Configuration is a server address, a pre-shared key or certificate and user credentials, entered into the OS's built-in VPN client. Because it encapsulates twice it is slower than IKEv2 or WireGuard, and its fixed ports make it easy to block. Support remains universal, which keeps it alive as a fallback option.