PoE: An AP Cannot Be Powered On Using PoE

Symptom

An AP cannot be powered on using PoE.

Possible Causes

• The AP and switch do not comply with the same PoE standard.
• The switch is not properly grounded.
• The PoE function is disabled on the switch.
• The remaining output power of the switch is insufficient.
• The network cable is faulty.

Procedure

The typical troubleshooting procedure for this fault is as follows:

1. Check whether the PSE and AP comply with the same PoE standard.
   1. Determine the PoE standard supported by the AP.
   2. Determine the PoE standard supported by the PSE. The following method applies only to Huawei PoE switches. Run the display poe power command in the system view.

      <Switch> display poe power
      Codes: REFPW(Reference power), USMPW(User set max power),
             CURPW(Current power), PKPW(Peak power), AVGPW(Average power)
      
      PortName               Class  REFPW(mW) USMPW(mW) CURPW(mW) PKPW(mW)  AVGPW(mW) 
      ------------------------------------------------------------------------------
      GigabitEthernet0/0/1   -      -         30000     0         0         0   

      Check the value of the USMPW field.

      • The value 15400 indicates that the switch supports IEEE 802.3af.
      • The value 30000 indicates that the switch supports IEEE 802.3at.

      Check whether the switch and AP comply with the same PoE standard. If not, replace the switch with a PoE switch in compliance with the same PoE standard as the AP.

2. Check whether the switch is properly grounded.

   Check whether the switch shell is properly grounded according to the switch installation guide.

3. Check whether the PoE function is enabled on the switch.

   The following method applies only to Huawei PoE switches.

   [Switch] display poe power-state interface gigabitEthernet 0/0/3 
    Port legacy detect           : disable 
    Port power enabled           : Disable 
    Port power ON/OFF            : off

   If the Port power enabled field is Disable, enable the PoE function in the interface view.

   <Switch> system-view 
   Enter system view, return user view with Ctrl+Z. 
   [Switch] interface GigabitEthernet 0/0/3 
   [Switch-GigabitEthernet0/0/3] poe enable 
   [Switch-GigabitEthernet0/0/3] quit 
   [Switch] quit

4. Check whether the remaining power of the switch is sufficient.

   The following method applies only to Huawei PoE switches.

   <Switch> display poe information
   PSE Information of slot 0:
   User Set Max Power(mW): 739200
   POE Power Supply(mW)       : 369600
   Available Total Power(mW)   : 369600
   Total Power Consumption(mW) : 0
   Power Peak Value(mW)       : 0
   Power-Management Mode      : auto
   Power High Inrush          : disable

   Check whether the value of the Available Total Power field meets the AP power requirement.

   Table 5-1 AP power requirements

   AP PoE Standard	Available Total Power
   IEEE 802.3af/at	≤ 15400
   IEEE 802.3af	≤ 15400
   IEEE 802.3at	≤ 30000
   IEEE 802.3bt	≤ 90000

   If the value of the Available Total Power field is smaller than the required AP power, increase the power of the switch or power off idle PDs on the switch.

5. Check whether the network cables comply with PoE standards.
   A network cable tester or multimeter is typically used to check network cable quality.

   Table 5-2 Network cable quality required by PoE standards

   Standard		Total Resistance of a Network Cable
   802.3af		≤ 20 ohms
   802.3at	Type 1	≤ 20 ohms
   	Type 2	≤ 12.5 ohms
   802.3bt		≤ 12.5 ohms

   The resistance of a network cable can be tested using the following methods:

   • Method 1

     Use a network cable tester to test the resistance of a network cable.

   • Method 2

     Connect test probes of a multimeter to the two ends of each network cable, and read the resistance value of the network cable on the multimeter. The cable resistance approximately equals the displayed value.

   • Method 3

     Connect a network cable to an AP. Use a multimeter to test the resistance between pins 1 and 2 of the cable (or between pins 3 and 6, 4 and 5, or 7 and 8). The cable resistance approximately equals half of the displayed value.

   If the resistance of a network cable does not meet requirements of PoE standards, replace the network cable.