L2TP/IPsec
L2TP tunnels the traffic; IPsec supplies the security.
How widely is it used?
Still around, but being replacedKept alive purely by old hardware and OS built-in clients.
How it works
L2TP builds the tunnel but provides no encryption of its own, so it is paired with an IPsec transport-mode association that protects it — usually authenticated with a shared secret.
Connects
Device → VPN gateway
Protocols
L2TP, IPsec
Typical users
Compatibility-driven deployments
Main use case
Remote access on older equipment that offers nothing better.
Advantages
- Built into almost every operating system ever shipped
- No client to install
Limitations
- Double encapsulation wastes bandwidth
- Fragile behind NAT
- Shared-secret setups are frequently weak