Cisco Wireless LAN Controller Configuration Guide, Release 7.4
Configuring Power Over Ethernet
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Configuring Power Over Ethernet

Configuring Power Over Ethernet

Information About Configuring Power over Ethernet

When an access point that has been converted to lightweight mode (such as an AP1131 or AP1242) or a 1250 series access point is powered by a power injector that is connected to a Cisco pre-Intelligent Power Management (pre-IPM) switch, you need to configure Power over Ethernet (PoE), also known as inline power.

The dual-radio 1250 series access points can operate in four different modes when powered using PoE:

  • 20.0 W (Full Power)—This mode is equivalent to using a power injector or an AC/DC adapter.
  • 16.8 W—Both transmitters are used but at reduced power. Legacy data rates are not affected, but the M0 to M15 data rates are reduced in the 2.4-GHz band. Throughput should be minimally impacted because all data rates are still enabled. The range is affected because of the lower transmit power. All receivers remain enabled.
  • 15.4 W—Only a single transmitter is enabled. Legacy data rates and M0 to M7 rates are minimally affected. M8 to M15 rates are disabled because they require both transmitters. Throughput is better than that received with legacy access points but less than the 20 and 16.8 W power modes.
  • 11.0 W (Low Power)—The access point runs, but both radios are disabled.
The following are some guidelines for Power over Ethernet:
  • When a dual-radio 1250 series access point is powered using 15.4-W PoE, it cannot operate at full functionality, which requires 20 W. The access point can operate with dual radios on 15.4-W PoE, but performance is reduced in terms of throughput and range. If full functionality is required on 15.4 W, you can remove one of the radios from the 1250 series access point chassis or disable it in controller software release 6.0 or later releases so that the other radio can operate in full 802.11n mode. After the access point radio is administratively disabled, the access point must be rebooted for the change to take effect. The access point must also be rebooted after you reenable the radio to put it into reduced throughput mode. These modes provide the flexibility of running the 1250 series access points with the available wired infrastructure to obtain the desired level of performance. With enhanced PoE switches (such as the Cisco Catalyst 3750-E Series Switches), the 1250 series access points can provide maximum features and functionality with a minimum total cost of ownership. Alternatively, if you decide to power the access point with the existing PoE (802.3af) switches, the access point chooses the appropriate mode of operation based on whether it has one radio or two.

    Note


    For more information on the Cisco PoE switches, see this URL: 
http:/​/​www.cisco.com/​en/​US/​prod/​switches/​epoe.html


    • The table below shows the maximum transmit power settings for 1250 series access points using PoE.
    Table 1 Maximum Transmit Power Settings for 1250 Series Access Points Using PoE

    Radio Band

    Data Rates

    Number of Transmitters

    Cyclic Shift Diversity (CSD)

    Maximum Transmit Power (dBm)

    802.3af Mode (15.4 W)

    ePoE Power Optimized Mode (16.8 W)

    ePoE Mode (20 W)

    2.4 GHz

    802.11b

    1

    20

    20

    20

    802.11g

    1

    17

    17

    17

    802.11n MCS 0-7

    1

    2

    Disabled

    Enabled (default)

    17

    Disabled

    17

    14 (11 per Tx)

    17

    20 (17 per Tx)

    802.11n MCS 8-15

    2

    Disabled

    14 (11 per Tx)

    20 (17 per Tx)

    5 GHz

    802.11a

    1

    17

    17

    17

    802.11n MCS 0-7

    1

    2

    Disabled

    Enabled (default)

    17

    Disabled

    17

    20 (17 per Tx)

    17

    20 (17 per Tx)

    802.11n MCS 8-15

    2

    Disabled

    20 (17 per Tx)

    20 (17 per Tx)

    1 Maximum transmit power varies by channel and according to individual country regulations. See the product documentation for specific details.
  • When powered with a non-Cisco standard PoE switch, the 1250 series access point operates under 15.4 Watts. Even if the non-Cisco switch or midspan device is capable of providing higher power, the access point does not operate in enhanced PoE mode.

Configuring Power over Ethernet (GUI)


    Step 1   Choose Wireless > Access Points > All APs and then the name of the desired access point.
    Step 2   Choose the Advanced tab to open the All APs > Details for (Advanced) page.

    The PoE Status text box shows the power level at which the access point is operating: High (20 W), Medium (16.8 W), or Medium (15.4 W). This text box is not configurable. The controller auto-detects the access point’s power source and displays the power level here.

    Note   

    This text box applies only to 1250 series access points that are powered using PoE. There are two other ways to determine if the access point is operating at a lower power level. First, the “Due to low PoE, radio is transmitting at degraded power” message appears under the Tx Power Level Assignment section on the 802.11a/n (or 802.11b/g/n) Cisco APs > Configure page. Second, the “PoE Status: degraded operation” message appears in the controller’s trap log on the Trap Logs page.

    Step 3   Perform one of the following:
    • Select the Pre-standard 802.3af switches check box if the access point is being powered by a high-power 802.3af Cisco switch. This switch provides more than the traditional 6 Watts of power but do not support the intelligent power management (IPM) feature.
    • Unselect the Pre-standard 802.3af switches check box if power is being provided by a power injector. This is the default value.
    Step 4   Select the Power Injector State check box if the attached switch does not support IPM and a power injector is being used. If the attached switch supports IPM, you do not need to select this check box.
    Step 5   If you selected the Power Injector State check box in the previous step, the Power Injector Selection and Injector Switch MAC Address parameters appear. The Power Injector Selection parameter enables you to protect your switch port from an accidental overload if the power injector is inadvertently bypassed. Choose one of these options from the drop-down list to specify the desired level of protection:
    • Installed—This option examines and remembers the MAC address of the currently connected switch port and assumes that a power injector is connected. Choose this option if your network contains older Cisco 6-Watt switches and you want to avoid possible overloads by forcing a double-check of any relocated access points. If you want to configure the switch MAC address, enter the MAC address in the Injector Switch MAC Address text box. If you want the access point to find the switch MAC address, leave the Injector Switch MAC Address text box blank.
      Note   

      Each time an access point is relocated, the MAC address of the new switch port fails to match the remembered MAC address, and the access point remains in low-power mode. You must then physically verify the existence of a power injector and reselect this option to cause the new MAC address to be remembered.

    • Override—This option allows the access point to operate in high-power mode without first verifying a matching MAC address. You can use this option if your network does not contain any older Cisco 6-W switches that could be overloaded if connected directly to a 12-W access point. The advantage of this option is that if you relocate the access point, it continues to operate in high-power mode without any further configuration. The disadvantage of this option is that if the access point is connected directly to a 6-W switch, an overload occurs.
    Step 6   Click Apply.
    Step 7   If you have a dual-radio 1250 series access point and want to disable one of its radios in order to enable the other radio to receive full power, follow these steps:
    1. Choose Wireless > Access Points > Radios > 802.11a/n or 802.11b/g/n to open the 802.11a/n (or 802.11b/g/n) Radios page.
    2. Hover your cursor over the blue drop-down arrow for the radio that you want to disable and choose Configure.
    3. On the 802.11a/n (or 802.11b/g/n) Cisco APs > Configure page, choose Disable from the Admin Status drop-down list.
    4. Click Apply.
    5. Manually reset the access point in order for the change to take effect.
    Step 8   Click Save Configuration.

    Configuring Power over Ethernet (CLI)

    Use these commands to configure and See PoE settings using the controller CLI:

    • If your network contains any older Cisco 6-W switches that could be accidentally overloaded if connected directly to a 12-W access point, enter this command: config ap power injector enable {Cisco_AP | all} installed The access point remembers that a power injector is connected to this particular switch port. If you relocate the access point, you must reissue this command after the presence of a new power injector is verified.

      Note


      Ensure CDP is enabled before entering this command. Otherwise, this command will fail. See the Configuring the Cisco Discovery Protocol section for information about enabling CDP.


    • Remove the safety checks and allow the access point to be connected to any switch port by entering this command: config ap power injector enable {Cisco_AP | all} override You can use this command if your network does not contain any older Cisco 6-W switches that could be overloaded if connected directly to a 12-W access point. The access point assumes that a power injector is always connected. If you relocate the access point, it continues to assume that a power injector is present.
    • If you know the MAC address of the connected switch port and do not want to automatically detect it using the installed option, enter this command: config ap power injector enable {Cisco_AP | all} switch_port_mac_address
    • If you have a dual-radio 1250 series access point and want to disable one of its radios in order to enable the other radio to receive full power, enter this command: config {802.11a | 802.11b} disable Cisco_AP

      Note


      You must manually reset the access point in order for the change to take effect.


    • See the PoE settings for a specific access point by entering this command: show ap config general Cisco_AP Information similar to the following appears:
      
      Cisco AP Identifier.............................. 1
      Cisco AP Name.................................... AP1
      ...
      PoE Pre-Standard Switch.......................... Enabled
      PoE Power Injector MAC Addr...................... Disabled
      Power Type/Mode.................................. PoE/Low Power (degraded mode)
      ...

      
      The Power Type/Mode text box shows “degraded mode” if the access point is not operating at full power.
    • See the controller’s trap log by entering this command: show traplog If the access point is not operating at full power, the trap contains “PoE Status: degraded operation.”
    • You can power an access point by a Cisco prestandard 15-W switch with Power over Ethernet (PoE) by entering this command: config ap power pre-standard {enable | disable} {all | Cisco_AP}
      A Cisco prestandard 15-W switch does not support intelligent power management (IPM) but does have sufficient power for a standard access point. The following Cisco prestandard 15-W switches are available:
      • WS-C3550, WS-C3560, WS-C3750
      • C1880
      • 2600, 2610, 2611, 2621, 2650, 2651
      • 2610XM, 2611XM, 2621XM, 2650XM, 2651XM, 2691
      • 2811, 2821, 2851
      • 3631-telco, 3620, 3640, 3660
      • 3725, 3745
      • 3825, 3845
      The enable version of this command is required for full functionality when the access point is powered by a Cisco prestandard 15-W switch. It is safe to use if the access point is powered by either an IPM switch or a power injector or if the access point is not using one of the 15-W switches listed above.
      You might need this command if your radio operational status is "Down" when you expect it to be "Up." Enter the show msglog command to look for this error message, which indicates a PoE problem:
      
      Apr 13 09:08:24.986 spam_lrad.c:2262 LWAPP-3-MSGTAG041: AP 00:14:f1:af:f3:40 is unable to 
      verify sufficient in-line power. Radio slot 0 disabled.