To use openconnect in Ubuntu 15.10 you have to set a default route to the tun0 device that is opened up. Otherwise no traffic will be routed through the tunnel. To do so:
sudo openconnect https://yourvpn.com
wait until the connect banner passes and openconnect displays:
Connected tun0 as ##.###.###.##, using SSL
Then open a new tab on the console or put openconnect in the background. Enter
sudo route add default gw ##.###.###.## tun0
This will route all outgoing traffic to the default gateway which is your tunnel.
Theres a bug opened up in ubuntu launchpad. While it is being investigated/fixed you can use above hack to still use VPN with openconnect.
Bug: network-manager-openconnect / 1502847
Via: openconnect-vpn-setup-is-failing-in-ubuntu-15-10
Hi, Thomas. I tried your above mentioned hack, but the problem that I am facing is that though I am connected to the VPN but I’m unable to get access to the server. The connection gets closed from the server end as it takes too long to log-in into the server (times out). I also noticed that if I used gnome’s GUI to switch on the VPN, then my internet also kind of stops working. I’m unable to use the browser even to surf the pages. But if I add a route to the new IP exposed via openconnect from the terminal then I don’t get the problem of slowing of internet, but still access to the server is not possible. Any ideas as to what might be happening in this case? Thanks in advance