The IEEE 802.11 standard contains virtually no criteria by which a WLAN client should select the access point for a connection. While there are general guidelines according to which preference is given to an access point with a higher RSSI value (i. e. the received signal strength), for example, WLAN clients do not, in practice, adhere strictly to these definitions or the general guidelines. If both 2.4GHz and 5GHz are used to broadcast an SSID, there is normally no way of influencing the client as regards the preferred frequency band.
The steering of WLAN clients is based on the principle that many clients determine the available access points by means of an active scan. Active scanning here means that a client sends probe requests containing the network ID to which the client is to connect. Access points with this ID then send a test response, enabling the client to create a list of available access points. The vast majority of WLAN clients only connect to access points from which they have received a probe response, and this can be used to steer their selection process.
There are multiple, sometimes very advanced, criteria for steering. One of these criteria relates to the wireless frequency ranges used for client communication. Modern dual-band WLAN clients are expected to prefer the 5GHz frequency band over the (now) overcrowded 2.4GHz band. Band steering is the term given to purposefully assigning a WLAN client a particular frequency band or range.
The list of detected or "seen" clients contains all clients from which the access point has received a test request packet. In combination with the radio frequency on which the WLAN client sends the test request, this list is one of the bases on which the access point decides whether to respond to the request or not.
Other criteria depend on the reported client IDs and the configuration of the devices. It may be the case, for example, that fewer SSIDs are reported on the preferred frequency band than are on the one with the lower preference. Similarly, too low a transmit strength when SSIDs are reported can result in the client not receiving any probe responses at all on the preferred frequency band. For the latter scenario, it is important to ensure that the access point does not suppress probe responses on the less favored frequency band. The minimum signal strength responsible here can be set in the following ways :
- LANconfig:
- WEBconfig:
In LANconfig you can use to enable and manage the access point's band steering function.