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:
switch(config)# no interface 1 power
switch(config)# interface 1 power
PoE/PoE+ allocation using LLDP information
LLDP with PoE
When using PoE, enabling poe-lldp-detect allows automatic power configuration if the link partner supports
PoE. When LLDP is enabled, the information about the power usage of the PD is available, and the switch can
then comply with or ignore this information. You can configure PoE on each port according to the PD (IP phone,
wireless device, and so on) specified in the LLDP field. The default configuration is for PoE information to be
ignored if detected through LLDP.
NOTE:
Detecting PoE information via LLDP affects only power delivery; it does not affect normal Ethernet
connectivity.
Enabling or disabling ports for allocating power using LLDP
Syntax:
int <port-list> poe-lldp-detect [enabled | disabled]
Enables or disables ports for allocating PoE power based on the link-partner's capabilities via LLDP.
Chapter 4 Power Over Ethernet (PoE/PoE+) Operation 93
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