The switch will detect a Cisco Pre-standard or an IEEE-compliant PD when the PoE is enabled and the connected device is not being powered by an AC adapter.

After device detection, the switch determines the power requirements based on power classification class. Depending on the available power in the power budget, the switch determines if a port can be powered. The switch initially allocates this power when it detects and powers the device. Power negotiation using CDP/LLDP protocols happens thereafter. Maximum power budget for 4 LAN ports combined at any time is 30W x4 = 120W. On reload the PoE ports are powered down.(i.e they are powered down at rommon stage).

Power Management

Limit the PoE budget to prevent excess power consumption that may exceed the capacity of the power source.

To limit the PoE budget, configure the overall PoE budget using the power inline wattage max <watts-for-PSU> command in global configuration mode.

Note

The switch needs a minimum wattage of power to run efficiently. The power budget for PoE is calculated as the total power of the PSU minus the minimum wattage. For example, if the PSU can provide 170W of power and needs a minimum of 20W of power to run the switch, then the maximum PoE budget that can be configured is 150W.

This section describes the CLI to use for configuring and displaying PoE.

Before you configure Power over Ethernet (PoE), note the following:

• show inventory and show diag commands will not display details of the vendor/system integrator's PoE controller.

• show run command will not reflect the current PoE configuration.

• On connecting a PD, power negotiation happens almost instantly. However, it takes 3-5 minutes to reflect accurate statistics using show power inline

• The default software mode is PoE and not PoE+ to prevent overdraw.

• There is limited support for LLDP-MED and LLDP-MDI.

Note	Implementation of PoE is a partner option. The integrator is responsible for proper implementation into the finished product, therefore, it may or may not be available.

To configure auto or off:

power inline auto | never
 

switch#config terminal
switch#interface g0/1/<1,2,3,4>
switch(config-if)#power inline {auto|never} 

To enable CDP:

switch#config terminal
switch(config)#cdp run
switch(config#exit

To enable LLDP:

switch#config terminal
switch(config)#lldp run
switch(config#exit

To Verify your configuration:

switch#show power inline
Available:120.0(w)  Used:21.1(w)  Remaining:98.9(w)

Interface Admin  Oper       Power   Device              Class Max
                            (Watts)                            
--------- ------ ---------- ------- ------------------- ----- ----
Gi0/1/0   auto   on         14.7    IP Phone 8865       4     30.0 
Gi0/1/1   auto   on         6.3     IP Phone 8811       2     30.0 
Gi0/1/2   auto   off        0.0     n/a                 n/a   30.0 
Gi0/1/3   auto   off        0.0     n/a                 n/a   30.0 
switch#

To show power on a particular interface:

switch#show power inline {interface-id}

Displays PoE status for a switch for the specified interface.

show power inline interface-id detail
 

To show power consumption:

switch#show power
Main PSU :
    Total Power Consumption from 3.3V Line : 0.36
    Total Power Consumption from 5V Line : 6.20
    Configured Mode : N/A
    Current runtime state same : N/A
    PowerSupplySource : External PS
POE Module :
    Configured Mode : N/A
    Current runtime state same : N/A
    Total power available : 120 Watts
switch#

The list of commands for debugging PoE follows: