There is a better way I just did not post it. It is also posted at my wiki (https://wiki.hackspherelabs.com/index.php?title=U620L_Novatel#U620L_-_Set_CDC-ECM_Permanently):
=U620L=
==Put into CDC-ECM Mode==
Go to: http://192.168.1.1/fieldtest/
Click Debug Mode
You will have to restart your modem so unplug and re plug I usually wait at least 10 seconds before unplugging and 15-30 seconds before plugging back in
By default the modem will not work in Windows as Windows does not like this mode. Plug into a linux box or BSD box though and ask for a DHCP request and everything is cool!
You should still be able to access the web interface after this.
==Take out of CDC-ECM Mode==
Plug into linux box or a box that interacts with CDC-ECM mode.
Grab a DHCP release so we have access to the correct network (I think it uses NAT redirection)
Go to: http://192.168.1.1/fieldtest/
Click End User Mode
==Research Study==
I hope that they do not disable this feature in an update. I also wonder if having the modem in diagnostic mode disables firmware upgrades so I am going to track some firmware versions:
===Modem A===
Current Software Version:
1.3 (L1.218.1 M9x25MET-2.44.3 1 [2015-05-13 13:56:54])
Configuration Version:
I14.NVT,USB620.0
===Modem S===
Current Software Version:
1.3 (L1.218.1 M9x25MET-2.44.3 1 [2015-05-13 13:56:54])
Configuration Version:
I14.NVT,USB620.0
==Notes==
*I do not see a way to tell if the device is in debug mode
**This also gives you serial access too: screen /dev/ttyACM0 115200
**I do not know the password