ZyXEL Communications ZyWALL USG Series Application Notes page 103

Note: The Network Selection is set to auto by default. This means that the 3G USB
modem may connect to another 3G network when your service provider is not in
range or when necessary. Select Home to have the 3G device connect only to your
home network or local service provider . This prevents you from being charged using
the rate of a different ISP .
Go to the Dashboard. The Interface Status Summary section should contain a "cellular" entry.
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When its connection status is Connected you can use the 3G connection to access the Internet.
The USG automatically adds the cellular interface to the system default WAN trunk. If the USG is
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using a user-configured trunk as its default trunk and you want this cellular interface to be part of it,
use the Trunk screens to add it.
This way the USG can automatically balance the traffic load amongst the available WAN connections
to enhance overall network throughput. Plus, if a WAN connection goes down, the USG still sends
traffic through the remaining WAN connections. For a simple test, disconnect all of the USG's wired
WAN connections. If you can still access the Internet, your cellular interface is properly configured
and your cellular device is working.
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