Wi-Fi clients generally experience better performance when connected to the 5GHz band rather than the 2.4GHz band. This is because more channels are available, resulting in less co-channel contention, and generally more interference sources are present in the 2.4GHz band. It is therefore desirable to have 5GHz capable Wi-Fi clients connect on the 5GHz band.
There are a number of methodologies which can help to steer devices to the 5GHz band:
5GHz only SSID
This is the preferred method. Broadcasting an SSID in only the 5GHz band guarantees that all clients will connect at 5GHz. This is the only way to 100% guarantee that all 5GHz capable clients connect at 5GHz. This is recommended for corporate SSIDs, where all corporate devices are purchased by the business, and it can be confirmed that all devices are 5GHz capable. If a business has a few 2.4GHz only devices, a second corporate SSID, with a different name, “corp-legacy” for example, could be created just for those devices and advertised only across the 2.4GHz band
Certain Wi-Fi networks, created to support guest, BYOD and IoT, cannot guarantee that all devices will be 5GHz capable and therefore will require the SSID to be advertised in both bands. For these networks, there is still a desire to see 5GHz capable devices connect at 5GHz. Many clients will simply connect to whichever BSS is strongest, and this is often one in the 2.4GHz band. By tuning the transmit power settings, we can sway this decision towards the 5GHz band. Configuring the 5GHz radios to be 6dB stronger than the 2.4GHz radios can help to do this.
Mist provides the option to enable band steering for SSIDs which are operating on both the 2.4GHz and 5GHz band. Band steering encourages 5GHz capable devices to connect to 5GHz radios. When band steering is enabled Mist will try and identity those devices which are dual band capable, it will then supress 2.4GHz probe responses for those devices. So that, during active scanning, devices will only discover the 5GHz radios.
While band steering to 5GHz can help, it will never be 100% successful as clients will still be able to hear beacon frames from the 2.4GHz radios and can sometimes connect to these.