Hi nwmurphy,
There is a Network Watchdog Timer: Wan/Cellular->General->Interface priority.
Change the Network Watchdog Timer from disable to a time frame from the drop down list.
If there is no WAN connection for the time configured in this field, the gateway reboots.
There is a keep alive but it pings the ALMS to confirm an IP connection.
Services->ALMS
In addition, there is the AT commands:
*IPPING
*IPPINGADDR
*IPPINGFORCE
The settings are on the page 442 of the guide.
Thanks,
Jay