Comment 4 for bug 1513437

I'm having a similar issue I just upgrade to 15.10 from 14.04 and I started having the same issue. I would connect from the CLI using vpnc-connect and my saved profile. However once connect I would not be able to access any resource on the other side of the tunnel. It appeared to be a routing error but I had no way of confirming that.

In an effort to solve this I installed nm-applet-vpnc and connected with it and everything worked correctly. I took a look at the routes using netstat -r and there was a sicrepancy.

netstat -r after connect from CLI
$ netstat -r
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
default 10.0.0.1 0.0.0.0 UG 0 0 0 wlan0
10.0.0.0 * 255.255.255.0 U 0 0 0 wlan0
link-local * 255.255.0.0 U 0 0 0 wlan0
<TUNNEL IP> * 255.255.255.240 U 0 0 0 tun0
<MYPORTAL> 10.0.0.1 255.255.255.255 UGH 0 0 0 wlan0

netstat -r after connect using nm-applet-vpnc
$ netstat -r
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
default * 0.0.0.0 U 0 0 0 tun0
default 10.0.0.1 0.0.0.0 UG 0 0 0 wlan0
10.0.0.0 * 255.255.255.0 U 0 0 0 wlan0
link-local * 255.255.0.0 U 0 0 0 wlan0
<TUNNEL IP> * 255.255.255.240 U 0 0 0 tun0
<MYPORTAL> 10.0.0.1 255.255.255.255 UGH 0 0 0 wlan0

I ran
 sudo route add default tun0
Now netstat -r looks correct
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
default * 0.0.0.0 U 0 0 0 tun0
default 10.0.0.1 0.0.0.0 UG 0 0 0 wlan0
10.0.0.0 * 255.255.255.0 U 0 0 0 wlan0
link-local * 255.255.0.0 U 0 0 0 wlan0
<TUNNEL IP> * 255.255.255.240 U 0 0 0 tun0
<MYPORTAL> 10.0.0.1 255.255.255.255 UGH 0 0 0 wlan0

And now everything is working correctly.
However it would be much preferred to not have to manual add the default route once the vpn connection is up.

FYI janl I can get the nm-applet-vpnc to prompt me for dual factor authentication.