VPN fails: Could not find source connection

I am running Ubuntu 18.04 and trying to get a VPN (L2TP/IPSec) connection to my company. The necessary tools are already installed and I have a profile with the correct access data. However, if I try to activate the VPN with nmcli c up VPN it quits with the following error: Error: Connection activation failed: Could not find source connection. If I do a nmcli device status I get: DEVICE TYPE STATE CONNECTION br0 bridge connected br0 virbr0 bridge connected virbr0 eno1 ethernet connected eno1 lo loopback not managed -- virbr0-nic tun not managed -- **EDIT:** Here on StackExchange, there is similar issue , with two possible solutions. Both don't work for me. Let me explain: The 1st solution suggests to set 127.0.0.1 as default route. The only way for me to do so, is to set the default route of br0. But then I loose the IPv4 connection until the next restart. Changing the default route back, does not get the connection back online. The 2nd solution suggests to setup a netplan config. If I do so, I overcome the Could not find source connection.-Error, but I loose complete network access as well (until next reboot). So these are no working solutions for me. So I hope someone is able to help me. Thanks. **EDIT 2:** So apparently, I missunderstood the 1st provided solution - the default route. ip r gives me the following output: default via 10.1.10.1 dev br0 10.1.0.0/16 dev br0 proto kernel scope link src 10.1.20.25 169.254.0.0/16 dev br0 scope link metric 1000 192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown If I understand this correctly, br0 is the default route!? netstat -rn gives me the following output: Kernel-IP-Routentabelle Ziel Router Genmask Flags MSS Fenster irtt Iface 0.0.0.0 10.1.10.1 0.0.0.0 UG 0 0 0 br0 10.1.0.0 0.0.0.0 255.255.0.0 U 0 0 0 br0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 br0 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 And my etc/network/interfaces looks like this: # interfaces(5) file used by ifup(8) and ifdown(8) auto lo iface lo inet loopback auto br0 iface br0 inet dhcp bridge_ports eno1 bridge_stp off bridge_maxwait 0 bridge_fd 0 So right now I am not really sure what to do. As of my understanding the default route is set and [ifupdown] managed=true is set. So, what else could I do? I could try to get rid of that bridge, but I don't know if that would help. Thanks for any advice.