I’m running KDE on Debian 9 and L2TP VPNs don’t work out of the box. If I add an L2TP connection to NetworkManager and try to connect it says that I need to install
network-manager-l2tp, which isn’t packaged for Stretch. The good news is that the package in Debian unstable currently works just fine.
- Install dependencies
# apt install strongswan xl2tpd
- Download the package manually for your architecture at the bottom of this page: https://packages.debian.org/sid/network-manager-l2tp
- Install it
# dpkg -i network-manager-l2tp_1.2.8-1_amd64.deb
- Open NetworkManager settings
- Add “Layer 2 Tunneling Protocol” (the “IPsec” options are not the right ones for an ordinary L2TP/IPsec network)
- Enter details. If you are using a pre shared key for IPsec, note that it is okay to fill in only that field under IPsec Settings.
- Select VPN and hit Connect. It should just work.