Can you just try on different device to test the speed by connecting to both the primary network and Guest network using any one band 2.4 or 5G.

Also could you help me with the time of speed test performed before.

There is no harm in using guest network.

2.4ghz is a much slower network than 5ghz. 

Those speeds would indicate on the primary, you connected to 2.4ghz and the guest to the 5ghz. 

Are you using bandsteering? That allows devices to switch between the 2.4ghz/5ghz as needed. 

You can disable it or leave it, you just need to be aware when speedtesting, which band you’re connected to

I’ve tested on multiple devices (work laptop, home laptop, cell phone) and consistently gotten ~60Mbps on default network and ~300Mbps on guest. Am I bandsteering? I don’t think so, but the Surfboard Central app is confusing. Under “Main Wi-Fi Network,” “Enable Combined SSID across all Wi-Fi Bands” is set to false, and 5GHz is selected. Under “Guest Wi-Fi Network,” 5GHz is also selected.

When I look at the WiFi settings on my devices, they say they are attached to the Guest network. When I look at the Devices tab in the Surfboard Central app, it says these devices are on the 2.4GHz band.

Thank you both for the quick responses.

It is advised to switch the Wi-Fi channel and confirm that the network channels used at home and by guests are the same.

Restart the Wi-Fi module and reset the Wi-Fi defaults through GUI web portal.

QoS setting for Wi-Fi network prioritization. It is located at the bottom of the Wi-Fi > Networks screen. Network priorities: Should be disabled.

Finally got an Ethernet to USB-C adapter and was able to connect directly to the SURFboard. There it was easier to see the four distinct bands (2.4GHz and 5GHz on home and guest), and to tell which devices were on which one. I was able to get every device connected on the band where I wanted it. Thanks for help!