The IEEE 802.11 standard contains virtually no criteria by which a WLAN client should select the AP for a connection. While there are, for example, general guidelines for the preference given to an AP with a higher RSSI value (i.e. the received signal strength), WLAN clients do not, in practice, adhere strictly to these definitions or the general guidelines. If both 2.4 GHz and 5 GHz are used to broadcast an SSID, there is normally no way of influencing the client as regards the preferred frequency band.
WLAN "client steering" is based on the principle that many clients find the APs available to them 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. APs with this ID then send a test response, enabling the client to create a list of available APs. The vast majority of WLAN clients only connect to APs from which they have received a probe response, and this can be used to steer their selection process.
There are several, sometimes highly 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 5 GHz frequency band over the (now) overcrowded 2.4 GHz band. Band Steering is the term given to purposefully assigning a WLAN client to a particular frequency band or range.
The list of detected or "seen" clients contains all clients from which the AP has received a test request packet. In combination with the radio frequency on which the WLAN client sends the probe request, this list is one of the bases used by the AP to decide whether or not to respond to the request.
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 AP 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:
- Command line:
In LANconfig, band steering is activated for the access point under by selecting AP-based band steering and is administered under .
