I got 2 internet connections in my computer. One is using 3.5G HSDPA modem (vodafone huawei e220) and the other using mobile phone (cdma zte c261). Both are using different ISP and i have both.

at the moment, i can connect to my office vpn using the HSDPA modem one.

But when i tried to use cdma modem (dial up - mobile phone modem), i am just able to get "verifying username and password" and then after a few minutes it display error : Error 721 The Remote Computer didn't respond.

I tried to ping into my office ip address, it got good result but still cannot connect to the vpn. I tried to turn off all my firewall (i'm using commodo) and has no response as well.

In my cdma mobile phone modem Network connections I tried to allow iNternet connection sharing as well ... and turn on all Internet Protocol TCP/IP, File & Printer Sharing & Client for microsoft networks. But all of my effort has no effect.

How to fix this problem ?

note: my office using windows vpn as well.

thank you .