L2TPv3 (Layer Two Tunneling Protocol Version 3) is a protocol that enables Layer 2 point-to-point tunnels over a Layer 3 infrastructure.
This means you can tunnel L2 protocols like Ethernet, Frame-relay, ATM, HDLC, PPP, etc. over an IP network. This can be pretty useful…For example, let’s say you have two remote sites and an application that requires that hosts are on the same subnet. With L2TPv3, it’s no problem to “bridge” two remote sites together, putting them in the same broadcast domain/subnet.
L2TPv3 uses various parameters and technologies to achieve this, namely:
- protocol number 115
- UDP port 1701
- Cisco L2F (Layer 2 Forwarding)
- Microsoft Point to Point Tunneling Protocol (PPTP)*