Hello, I have a Vodafone K3772 3G dongle connected to my Vigor 2820Vn router. It connects fine, but only in GPRS mode, not 3G (though the 3G signal here is good).

I have a hunch that I have the wrong Modem Initialisation String or Modem Dial String as the dongle was working correctly on a previous 2820Vn (unfortunately/stupidly I did not capture the previous config).

Here are my current settings...

Modem Initial String: APN:smart
Modem Dial String: ATDT:*99#

Any help would be much appreciated.

UPDATE: If the router is rebooted, the dongle initially connects with 3G. If the internet connection is not used for a while (10 minutes say), the dongle drops back to GPRS and does not resume 3G once the connection is used again.