Configuring PoE operation

Disabling or re-enabling PoE port operation

Syntax:

[no] interface <port-list> power-over-ethernet

Re-enables PoE operation on <port-list> and restores the priority setting in effect when PoE was disabled on <port-list>.

The no form of the command disables PoE operation on <port-list>.

Default: All PoE ports are initially enabled for PoE operation at Low priority. If you configure a higher priority, this priority is retained until you change it.


	NOTE: For PoE, disabling all ports allows the 22 watts of minimum PoE power or the 38 watts for PoE+ power allocated for the module to be recovered and used elsewhere. You must disable ALL ports for this to occur.

Enabling support for pre-standard devices

The HP switches covered in this guide also support some pre-802.3af devices. For a list of the supported devices, see the FAQ for your switch model.

Syntax:

[no] power-over-ethernet pre-std-detect

Detects and powers pre-802.3af standard devices.


	NOTE: The default setting for the `pre-std-detect` PoE parameter has changed.

Configuring the PoE port priority

Syntax:

interface <port-list> power-over-ethernet [ critical | high | low ]

Reconfigures the PoE priority level on <port-list>. For a given level, ports are prioritized by port number in ascending order. For example, if ports 1-24 have a priority level of critical, port 1 has priority over ports 2-24.

If there is not enough power available to provision all active PoE ports at a given priority level, the lowest-numbered port at that level is provisioned first. For chassis switches, the lowest-numbered port at that level starting with module A, then B, C, and so on is provisioned. PoE priorities are invoked only when all active PoE ports cannot be provisioned (supplied with PoE power)

Critical Specifies the highest-priority PoE support for <port-list>. The active PoE ports at this level are provisioned before the PoE ports at any other level are provisioned.

High Specifies the second priority PoE support for <port-list>. The active PoE ports at this level are provisioned before the Low priority PoE ports are provisioned.

Low (Default) Specifies the third priority PoE support for <port-list>. The active PoE ports at this level are provisioned only if there is power available after provisioning any active PoE ports at the higher priority levels.

PoE priority operation on a PoE module shows some examples of PoE priority configuration.

PoE priority operation on a PoE module

Port	Priority setting	Configuration command^[a] and resulting operation with PDs connected to ports C3 through C24
C3 - C17	Critical	In this Example:, the following CLI command sets ports C3 to C17 to Critical: HP Switch(config)# interface c3-c17 power-over-ethernet critical The critical priority class always receives power. If there is not enough power to provision PDs on all ports configured for this class, no power goes to ports configured for high and low priority. If there is enough power to provision PDs on only some of the critical-priority ports, power is allocated to these ports in ascending order, beginning with the lowest-numbered port in the class, which, in this case, is port 3.
C18 - C21	high	In this Example:, the following CLI command sets ports C19 to C22 to high: HP Switch(config)# interface c19-c22 power-over-ethernet high The high priority class receives power only if all PDs on ports with a critical priority setting are receiving power. If there is not enough power to provision PDs on all ports with a high priority, no power goes to ports with a low priority. If there is enough power to provision PDs on only some of the high-priority ports, power is allocated to these ports in ascending order, beginning, in this Example:, with port 18, until all available power is in use.
C22 - C24	low	In this Example:, the CLI command sets ports C23 to C24 to low^[b]: HP Switch(config)# interface c23-c24 power-over-ethernet low This priority class receives power only if all PDs on ports with high and critical priority settings are receiving power. If there is enough power to provision PDs on only some low- priority ports, power is allocated to the ports in ascending order, beginning with the lowest-numbered port in the class (port 22, in this case), until all available power is in use.
C1 - C2	N/A	In this Example:, the CLI command disables PoE power on ports C1 to C2: HP Switch(config)# no interface c1-c2 power-over-ethernet There is no priority setting for the ports in this Example:.
^[a] For a listing of PoE configuration commands with descriptions, see Configuring PoE operation. ^[b] In the default PoE configuration, the ports are already set to low priority. In this case, the command is not necessary.

Controlling PoE allocation

Syntax:

[no] int <port-list> poe-allocate-by [ usage | class | value ]

Allows you to manually allocate the amount of PoE power for a port by either its class or a defined value.

The default option for PoE allocation is usage, which is what a PD attached to the port is allocated. You can override this value by specifying the amount of power allocated to a port by using the class or value options.

usage
(Default) The automatic allocation by a PD.

class
Uses the power ramp-up signature of the PD to identify which power class the device will be in. Classes and their ranges are shown in Power classes and their values.

value
A user-defined level of PoE power allocated for that port.


	NOTE: The allowable PD requirements are lower than those specified for PSEs to allow for power losses along the Cat-5 cable.

Power classes and their values

Power class	Value
0	Depends on cable type and PoE architecture. Maximum power level output of 15.4 watts at the PSE. This is the default class; if there is not enough information about the load for a specific classification, the PSE classifies the load as class 0 (zero).
1	Requires at least 4 watts at the PSE.
2	Requires at least 7 watts at the PSE.
3	15.4 watts
4	For PoE+ Maximum power level output of 30 watts at the PSE.

Example:

To allocate by class for ports 6 to 8:

HP Switch(config)# int 6-8 PoE-allocate-by class

Manually configuring PoE power levels

You can specify a power level (in watts) allocated for a port by using the value option. This is the maximum amount of power that will be delivered.

To configure a port by value:

Set the PoE allocation by entering the poe-allocate-by value command:

HP Switch(config) # int A6 poe-allocate-by value

or in interface context:

HP Switch(eth-A6) # poe-allocate-by value

Select a value:

HP Switch(config) # int A6 poe-value 15

or in interface context:

HP Switch(eth-A6) # poe-value 15

To view the settings, enter the show power-over-ethernet command, shown in PoE allocation by value and the maximum power delivered.

PoE allocation by value and the maximum power delivered

HP Switch(config)# show power-over-ethernet A6

 Status and Counters - Port Power Status for port A7

  Power Enable     : Yes
                                       LLDP Detect     : enabled
  Priority         : low               Configured Type :
  AllocateBy       : value             Value           : 15 W 


  Detection Status : Delivering        Power Class     : 2

  Over Current Cnt : 0                 MPS Absent Cnt  : 0
  Power Denied Cnt : 0                 Short Cnt       : 0

  Voltage          : 55.1 V            Current         : 154 mA
  Power            : 8.4 W

Maximum power delivered.

If you set the PoE maximum value to less than what the PD requires, a fault occurs, as shown in PoE power value set too low for the PD.

PoE power value set too low for the PD

HP Switch(config)# int A7 poe-value 4

HP Switch(config)# show power-over-ethernet A7

 Status and Counters - Port Power Status for port A7

  Power Enable     : Yes
                                       LLDP Detect     : enabled
  Priority         : low               Configured Type :
  AllocateBy       : value             Value           : 4 W
  Detection Status : fault 

            Power Class     : 2

  Over Current Cnt : 1                 MPS Absent Cnt  : 0
  Power Denied Cnt : 2                 Short Cnt       : 0

  Voltage          : 55.1 V            Current         : 154 mA
  Power            : 8.4 W

‘Fault’ appears when the PoE power value is set too low.

Changing the threshold for generating a power notice

By default, PoE support is enabled on the switch’s 10/100Base-TX ports, with the power priority set to Low and the power threshold set to 80 (%). The following commands allow you to adjust these settings.

Syntax:

power threshold <1-99>

The power threshold is a configurable percentage of the total PoE power available on the switch. When PoE consumption exceeds the threshold, the switch automatically generates an SNMP trap and also sends a message to the Event Log. For example, if the power threshold is set to 80% (the default), and an increasing PoE power demand crosses this threshold, the switch sends an SNMP trap and generates this Event Log message:
PoE usage has exceeded threshold of 80 %.
If the switch is configured for debug logging, it also sends the same message to the configured debug destination(s).

The switch automatically invokes the power threshold at the global configuration level with a default setting of 80%. You can configure the power threshold to a value in the range of 1% to 99%.

If an increasing PoE power load (1) exceeds the configured power threshold (which triggers the log message and SNMP trap), and then (2) later begins decreasing and drops below the threshold again, the switch generates another SNMP trap, plus a message to the Event Log and any configured Debug destinations. To continue the above Example:
PoE usage is below configured threshold of 80 %.

Cycling power on a port

Simply disabling a PoE port does not affect power delivery through that port. To cycle the power on a PD receiving power from a PoE port on the switch, disable, then re-enable the power to that port.

Syntax:

[no]interface [e]<port-list> power

Re-enables PoE operation on <port-list> and restores the priority setting in effect when PoE was disabled on <port-list>. The [no] form of the command disables PoE operation on <port-list>. (Default: All 10/100Base-TX ports on the switch enabled for PoE operation at Low priority.)

For example, to cycle the power on a PoE device connected to port 1 on a switch covered in this guide:

HP Switch(config)# no interface 1 power
HP Switch(config)# interface 1 power

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`Critical`	Specifies the highest-priority PoE support for `<port-list>`. The active PoE ports at this level are provisioned before the PoE ports at any other level are provisioned.
`High`	Specifies the second priority PoE support for `<port-list`>. The active PoE ports at this level are provisioned before the `Low` priority PoE ports are provisioned.
`Low`	(Default) Specifies the third priority PoE support for `<port-list>`. The active PoE ports at this level are provisioned only if there is power available after provisioning any active PoE ports at the higher priority levels.

`usage`	(Default) The automatic allocation by a PD.
`class`	Uses the power ramp-up signature of the PD to identify which power class the device will be in. Classes and their ranges are shown in Power classes and their values.
`value`	A user-defined level of PoE power allocated for that port.