L2TP is made by Microsoft and Apple. It does NOT provide encryption at all. IPSec does. Apple and Microsoft avoid telling people this. They reinvented the wheel, poorly. For my taste, I prefer Cisco's PPTP. But I have to live with it as my university uses it.
1. Ubuntu does not support L2TP in NetworkManager, the one you use to configure Ethernet and Wi-Fi. Don't panic. There is a good GUI to help you.
2. Please install Werner Jaeger's L2TP IPSec VPN Manager from https://launchpad.net/~werner-jaeger/+archive/ppa-werner-vpn/+packages Just download the ones for your Ubuntu version. You can tell from the Ubuntu codename at the end of package names. If you are not sure about the codenames of Ubuntu releases, check out https://wiki.ubuntu.com/DevelopmentCodeNames
3. If you have tried other L2TP/IPSec solutions you googled, you may need to reinstall the three packages.
4. After that, log out and re-log in. You shall see an icon, like two computers stacked together, on your Ubuntu system tray. Right (secondary) click it and select "Edit Connections..."
|Figure 1: L2TP IPSec VPN Manager on Ubuntu system tray|
|Figure 2: "VPN Connection" window|
|Figure 3: Name a new VPN connection|
vpn.ttu.edufor "Remote Server." For "User pre-shared key for authentication," enter
|Figure 4: Edit connection settings, IPSec tab|
|Figure 5: PPP settings for VPN|
Please feel free to tell me how poor this guide is written. You can use my pictures if you say "Courtesy of Forrest" - pictures and texts are licensed under CC license at the bottom of this page.