How to use both channels of a dual router

The Gateways come out-of-the box using both bands with the same SSID, a setup known a band steering.  The theory is that both 2.4 GHz and 5 GHz clients can connect, and a client capable of both can switch back and forth as conditions warrant.  In practice, many devices that are 2.4 GHz only get confused and fail to connect properly.  Client devices capable of both tend to connect to one band and stick to that, even when they should change, and sometimes change or disconnect for no apparent reason.  

If you wish, you can give the two bands different SSIDs, so that your 2.4 GHz devices can be directed to the 2.4 GHz SSID and not see a confusing 5 GHz band setup.  To do that, go to the Home Network tab, Wi-Fi subtab, and click Advanced Options.  You can scroll down to the SSID field of each band and change it as you wish.  If you change both, though, existing clients will need to be changed to one of the new SSIDs; if you leave one alone, then existing clients can continue to connect to that band using their current settings.  After doing this, click on Save.  You will get a warning about fire, floods, pestilence, war, etc. because you changed the SSIDs and have thus turned off Band Steering.  You may safely ignore this warning.