I use VPNC (the command line client from the package vpnc) to connect with my institution. The configuration file looks like this
IPSec ID CiscoGroup
IPSec gateway xxx.xxx.xxx
IPSec secret XXXXXXXX
IKE Authmode psk
NAT Traversal Mode cisco-udp
Xauth username xxxxxxx
The VPN connection works like a breeze if I use my wireless interface. However, if I am connected to the internet using a UMTS stick ("Lidl stick"), it no longer does. The UMTS alone is working -- I can use it to connect to the internet. The vpnc client gets started with no apparent errors, so it can approach and talk to the gateway and establish a connection. However, the moment it goes into background, I loose all connectivity.
This is not a DNS problem -- using IPs does not help.
Interestingly, I can still ping one and only server -- the gateway. Nothing else.
Is this a known problem? Is there a solution?
Ubuntu 14.04