VPN via Fritzbox in ubuntu
First you nbeed to install some packages:
sudo apt-get install network-manager-vpnc-gnome resolvconf dnsmasq openssh-server
In Dutch some extra explanation (use google translate):
https://nl.avm.de/service/knowledge-base/dok/FRITZ-Box-7590/3448_VPN-met-FRITZ/
Ubuntu 22.04 and Linux Mint 21 have an error in its connection manager.
In Linux Mint Debian Edition the same error occurs, but needs anorther solution.
Firts Ubuntu 22.04 and Linux Mint 21:
I found a working workaround in this thread:
The form validation seems buggy and there is a required field ("interface name") which was not required before. It is in the "Advanced" window.
There is a GUI workaround. Instead of editing the connection with the main Gnome Settings application, you have to do the following:
Launch Advanced Network Configuration (or run nm-connection-editor from terminal)
Click the "+" (Add a new connection), choose "Cisco Compatible VPN (vpnc)", click "Create..."
Fill all the fields
Click the "Advanced..." button
Fill "Tunnel interface name" with tun0
Click "Apply"
The Save button will still be disabled. Click "Advanced..." again and "Apply".
Finally, you will be able to "Save"!
This is tested on Ubuntu 22.04, Ubuntu budgie 22,04, Lubuntu 22.04, Pop!_OS 22.04, all with network-manager-vpnc-gnome version 1.2.8-2.
Linux Mint Debian edition needs 3 more packages to be installed. ( I already added them above, but other tutorials on the internet don't name them)
sudo apt install resolvconf dnsmasq openssh-server
It should work now.
Alas the quality of the VPN is not 100% is your default gateway at home is the same as on the other side of the VPN. Since I connect from an Fritzbox at home to a Fritzbox somewhere else, I cannot login the interface of that Fritzbox, unless I have a comupter over there that I can VNC into. e.g. a raspberry PI that is online.
My IP viewer still gives me my original IP nr, but I can make a VNC connection with a remote Raspberry PI as if is is locally connected. Strange.