L2TP (Layer 2 Tunneling Protocol) is a tunneling protocol used for VPNs. It uses the UDP port 1701 to communicate. It doesn’t have any encryption, but we can encrypt the L2TP packets by using it with IPSec. For theoretical information on L2TP you can visit its Wiki.
In Linux, you can find so many different applications to build a L2TP server but there is no proper documentation for this. Also, I think no one is using L2TP VPN nowadays. But my requirement could solve by L2TP only. I wanted to configure the VPN for some old devices that does support only L2TP VPN.
I use Centos 5 Linux for VPN server. For VPN application, I use the combination to two applications. One isxl2tpd & rp-l2tpd.
I also had the option of openl2tpd, I tried this on Fedora 8 Linux but there is some bug on fedora 8’s pppd, which stopped me to use that. And when I tried to install openl2tpd on Centos 5, it asked to enable the L2TP support on kernel. I didn’t want to play with kernel that time.
That was the reason, I switched to xl2tpd application. It is the same application l2tpd but maintained byXelerance Corporation. I don’t use l2tpd due to some compilation problem. I also face the compilation problem with xl2tpd, but it was manageable. You will also see the use of rp-l2tpd, it is also solving some dependency problem for xl2tpd.
keep reading in L2TP VPN using xl2tpd.