Cisco Wireless LAN Controller Configuration Guide, Release 7.5
Configuring 802.11 Bands
Downloads: This chapterpdf (PDF - 1.31MB) The complete bookPDF (PDF - 17.88MB) | The complete bookePub (ePub - 4.41MB) | Feedback

Configuring 802.11 Bands

Configuring 802.11 Bands

Configuring 802.11 Bands

Information About Configuring 802.11 Bands

You can configure the 802.11b/g/n (2.4-GHz) and 802.11a/n/ac (5-GHz) bands for the controller to comply with the regulatory requirements in your country. By default, both 802.11b/g/n and 802.11a/n/ac are enabled.

When a controller is configured to allow only 802.11g traffic, 802.11b client devices are able to successfully connect to an access point but cannot pass traffic. When you configure the controller for 802.11g traffic only, you must mark 11g rates as mandatory.

Configuring the 802.11 Bands (GUI)


    Step 1   Choose Wireless > 802.11a/n/ac or 802.11b/g/n > Network to open the Global Parameters page.
    Step 2   Select the 802.11a (or 802.11b/g) Network Status check box to enable the 802.11a or 802.11b/g band. To disable the band, unselect the check box. The default value is enabled. You can enable both the 802.11a and 802.11b/g bands.
    Step 3   If you enabled the 802.11b/g band in Step 2, select the 802.11g Support check box if you want to enable 802.11g network support. The default value is enabled. If you disable this feature, the 802.11b band is enabled without 802.11g support.
    Step 4   Specify the period at which the SSID is broadcast by the access point by entering a value between 20 and 1000 milliseconds (inclusive) in the Beacon Period text box. The default value is 100 milliseconds.
    Note   

    The beacon period in controllers is listed in terms of milliseconds. The beacon period can also be measured in time units, where one time unit equals 1024 microseconds or 102.4 milliseconds. If a beacon interval is listed as 100 milliseconds in a controller, it is only a rounded off value for 102.4 milliseconds. Due to hardware limitation in certain radios, even though the beacon interval is, say 100 time units, it is adjusted to 102 time units, which roughly equals 104.448 milliseconds. When the beacon period is to be represented in terms of time units, the value is adjusted to the nearest multiple of 17.

    Step 5   Specify the size at which packets are fragmented by entering a value between 256 and 2346 bytes (inclusive) in the Fragmentation Threshold text box. Enter a low number for areas where communication is poor or where there is a great deal of radio interference.
    Step 6   Make access points advertise their channel and transmit power level in beacons and probe responses for CCX clients. Select the DTPC Support check box. Otherwise, unselect this check box. The default value is enabled.

    Client devices using dynamic transmit power control (DTPC) receive the channel and power level information from the access points and adjust their settings automatically. For example, a client device used primarily in Japan could rely on DTPC to adjust its channel and power settings automatically when it travels to Italy and joins a network there.

    Note   

    On access points that run Cisco IOS software, this feature is called world mode.

    Note   

    DTPC and 801.11h power constraint cannot be enabled simultaneously.

    Step 7   Specify the maximum allowed clients by entering a value between 1 to 200 in the Maximum Allowed Client text box. The default value is 200.
    Step 8   Use the Data Rates options to specify the rates at which data can be transmitted between the access point and the client. These data rates are available:
    • 802.11a—6, 9, 12, 18, 24, 36, 48, and 54 Mbps
    • 802.11b/g—1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48, or 54 Mbps

    For each data rate, choose one of these options:

    • Mandatory—Clients must support this data rate in order to associate to an access point on the controller.
    • Supported—Any associated clients that support this data rate may communicate with the access point using that rate. However, the clients are not required to be able to use this rate in order to associate.
    • Disabled—The clients specify the data rates used for communication.
    Step 9   Click Apply.
    Step 10   Click Save Configuration.

    Configuring the 802.11 Bands (CLI)


      Step 1   Disable the 802.11a band by entering this command:

      config 802.11a disable network

      Note   

      The 802.11a band must be disabled before you can configure the 802.11a network parameters in this section.

      Step 2   Disable the 802.11b/g band by entering this command:

      config 802.11b disable network

      Note   

      The 802.11b band must be disabled before you can configure the 802.11b network parameters in this section.

      Step 3   Specify the rate at which the SSID is broadcast by the access point by entering this command:

      config {802.11a | 802.11b} beaconperiod time_unit

      where time_unit is the beacon interval in time units (TUs). One TU is 1024 microseconds. You can configure the access point to send a beacon every 20 to 1000 milliseconds.

      Step 4   Specify the size at which packets are fragmented by entering this command:

      config {802.11a | 802.11b} fragmentation threshold

      where threshold is a value between 256 and 2346 bytes (inclusive). Specify a low number for areas where communication is poor or where there is a great deal of radio interference.

      Step 5   Make access points advertise their channel and transmit power level in beacons and probe responses by entering this command:

      config {802.11a | 802.11b } dtpc {enable | disable}

      The default value is enabled. Client devices using dynamic transmit power control (DTPC) receive the channel and power level information from the access points and adjust their settings automatically. For example, a client device used primarily in Japan could rely on DTPC to adjust its channel and power settings automatically when it travels to Italy and joins a network there.

      Note   

      On access points that run Cisco IOS software, this feature is called world mode.

      Step 6   Specify the maximum allowed clients that can be configured by entering this command:

      config {802.11a | 802.11b} max-clients max_allow_clients

      The valid range is between 1 to 200.

      Step 7   Specify the rates at which data can be transmitted between the controller and the client by entering this command:

      config {802.11a | 802.11b} rate {disabled | mandatory | supported} rate

      where

      • disabled—Clients specify the data rates used for communication.
      • mandatory—Clients support this data rate in order to associate to an access point on the controller.
      • supported—Any associated clients that support this data rate may communicate with the access point using that rate. However, the clients are not required to be able to use this rate in order to associate.
      • rate—The rate at which data is transmitted:
        • 6, 9, 12, 18, 24, 36, 48, and 54 Mbps (802.11a)
        • 1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48, or 54 Mbps (802.11b/g)
      Step 8   Enable the 802.11a band by entering this command:

      config 802.11a enable network

      The default value is enabled.

      Step 9   Enable the 802.11b band by entering this command:

      config 802.11b enable network

      The default value is enabled.

      Step 10   Enable or disable 802.11g network support by entering this command:

      config 802.11b 11gSupport {enable | disable}

      The default value is enabled. You can use this command only if the 802.11b band is enabled. If you disable this feature, the 802.11b band is enabled without 802.11g support.

      Step 11   Enter the save config command to save your changes.
      Step 12   View the configuration settings for the 802.11a or 802.11b/g band by entering this command:

      show {802.11a | 802.11b}

      Information similar to the following appears:

      
      802.11a Network............................... Enabled
      11nSupport.................................... Enabled
            802.11a Low Band........................... Enabled
            802.11a Mid Band........................... Enabled
            802.11a High Band.......................... Enabled
      802.11a Operational Rates
          802.11a 6M Rate.............................. Mandatory
          802.11a 9M Rate.............................. Supported
          802.11a 12M Rate............................. Mandatory
          802.11a 18M Rate............................. Supported
          802.11a 24M Rate............................. Mandatory
          802.11a 36M Rate............................. Supported
          802.11a 48M Rate............................. Supported
          802.11a 54M Rate............................. Supported
      ...
      Beacon Interval.................................. 100
      ...
      Default Channel............................... 36
      Default Tx Power Level........................ 1
      DTPC Status................................... Enabled
      Fragmentation Threshold....................... 2346
      Maximum Number of Clients per AP................. 200
      
      

      Configuring Band Selection

      Information About Configuring Band Selection

      Band selection enables client radios that are capable of dual-band (2.4- and 5-GHz) operation to move to a less congested 5-GHz access point. The 2.4-GHz band is often congested. Clients on this band typically experience interference from Bluetooth devices, microwave ovens, and cordless phones as well as co-channel interference from other access points because of the 802.11b/g limit of three nonoverlapping channels. To prevent these sources of interference and improve overall network performance, you can configure band selection on the controller.

      Band selection is enabled globally by default.

      Band selection works by regulating probe responses to clients. It makes 5-GHz channels more attractive to clients by delaying probe responses to clients on 2.4-GHz channels.

      Restrictions on Band Selection

      • Band-selection enabled WLANs do not support time-sensitive applications like voice and video because of roaming delays.
      • Band selection can be used only with Cisco Aironet 1040, 1140, 1250, 1260, 3500, and the 3600 series access points.

        Note


        OEAP 600 Series access points do not support band select.


      • Band selection operates only on access points that are connected to a controller. A FlexConnect access point without a controller connection does not perform band selection after a reboot.
      • The band-selection algorithm directs dual-band clients only from the 2.4-GHz radio to the 5-GHz radio of the same access point, and it only runs on an access point when both the 2.4-GHz and 5-GHz radios are up and running.
      • You can enable both band selection and aggressive load balancing on the controller. They run independently and do not impact one another.
      • It is not possible to enable or disable band selection and client load balancing globally through the controller GUI or CLI. You can, however, enable or disable band selection and client load balancing for a particular WLAN. Band selection and client load balancing are enabled globally by default.

      Configuring Band Selection

      Configuring Band Selection (GUI)


        Step 1   Choose Wireless > Advanced > Band Select to open the Band Select page.
        Step 2   In the Probe Cycle Count text box, enter a value between 1 and 10. The cycle count sets the number of suppression cycles for a new client. The default cycle count is 2.
        Step 3   In the Scan Cycle Period Threshold (milliseconds) text box, enter a value between 1 and 1000 milliseconds for the scan cycle period threshold. This setting determines the time threshold during which new probe requests from a client come from a new scanning cycle. The default cycle threshold is 200 milliseconds.
        Step 4   In the Age Out Suppression (seconds) text box, enter a value between 10 and 200 seconds. Age-out suppression sets the expiration time for pruning previously known 802.11b/g/n clients. The default value is 20 seconds. After this time elapses, clients become new and are subject to probe response suppression.
        Step 5   In the Age Out Dual Band (seconds) text box, enter a value between 10 and 300 seconds. The age-out period sets the expiration time for pruning previously known dual-band clients. The default value is 60 seconds. After this time elapses, clients become new and are subject to probe response suppression.
        Step 6   In the Acceptable Client RSSI (dBm) text box, enter a value between –20 and –90 dBm. This parameter sets the minimum RSSI for a client to respond to a probe. The default value is –80 dBm.
        Step 7   Click Apply.
        Step 8   Click Save Configuration.
        Step 9   To enable or disable band selection on specific WLANs, choose WLANs > WLAN ID. The WLANs > Edit page appears.
        Step 10   Click the Advanced tab.
        Step 11   In the Load Balancing and Band Select text area, if you want to enable band selection, select the Client Band Select check box. If you want to disable band selection, leave the check box unselected. The default value is disabled.
        Step 12   Click Save Configuration.

        Configuring Band Selection (CLI)


          Step 1   Set the probe cycle count for band select by entering this command:

          config band-select cycle-count cycle_count

          You can enter a value between 1 and 10 for the cycle_count parameter.

          Step 2   Set the time threshold for a new scanning cycle period by entering this command:

          config band-select cycle-threshold milliseconds

          You can enter a value for threshold between 1 and 1000 for the milliseconds parameter.

          Step 3   Set the suppression expire to the band select by entering this command:

          config band-select expire suppression seconds

          You can enter a value for suppression between 10 to 200 for the seconds parameter.

          Step 4   Set the dual band expire by entering this command:

          config band-select expire dual-band seconds

          You can enter a value for dual band between 10 and 300 for the seconds parameter.

          Step 5   Set the client RSSI threshold by entering this command:

          config band-select client-rssi client_rssi

          You can enter a value for minimum dBm of a client RSSI to respond to a probe between 20 and 90 for the client_rssi parameter.

          Step 6   Enter the save config command to save your changes.
          Step 7   Enable or disable band selection on specific WLANs by entering this command:

          config wlan band-select allow {enable | disable} wlan_ID

          You can enter a value between 1 and 512 for wlan_ID parameter.

          Step 8   Verify your settings by entering this command:

          show band-select

          Information similar to the following appears:

          
          Band Select Probe Response....................... Enabled
             Cycle Count................................... 3 cycles
             Cycle Threshold............................... 300 milliseconds
             Age Out Suppression........................... 20 seconds
             Age Out Dual Band............................. 20 seconds
             Client RSSI................................... -30 dBm
          
          
          Step 9   Enter the save config command to save your changes.