I have set up a VPN network using the package https://github.com/nm-l2tp/NetworkManager-l2tp.
The VPN works well (on certain situations) but I think there's a problem with the routing.
When I'm not connected to any VPN, the routing table looks like this:
Routing table before connection
As soon as I connect to the VPN, my internet connection drops and my VPN starts working.
Routing table after connection
If I use the option "Use this connection only for resources on its network" the opposite happens: I have internet connection but it's like I'm not connected to the VPN.
Routing table after VPN using "local resources"
Is there something I can do on my client-side? By the way, using Windows to connect to this network doesn't make my internet connection to drop and everything works flawlessly.
UPDATE
Solved the issue! In fact, the whole problem was the routing table. I had to add an entry considering my VPN subnet 172.30.0.0, mask 255.255.255.0 and gateway pointing to my VPN gateway.
For future generations, it's better using other VPN than L2TP/IPsec on Linux distributions. It was much easier to set this on Windows/Mac environment.
PS: of course, I don't have a good network background but this guide made me understanding some basic stuff.
