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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 13 Configuring Interface Characteristics Configuring Ethernet Interfaces
For information about the output of the show power inline user EXEC command, see the command
reference for this release. For more information about PoE-related commands, see the “Troubleshooting
Power over Ethernet Switch Ports” section on page 51-13. For information about configuring voice
VLAN, see Chapter 17, “Configuring Voice VLAN.”
Budgeting Power for Devices Connected to a PoE Port
When Cisco powered devices are connected to PoE ports, the switch uses Cisco Discovery Protocol
(CDP) to determine the CDP-specific power consumption of the devices, and the switch adjusts the
power budget accordingly. This does not apply to IEEE third-party powered devices. For these devices,
when the switch grants a power request, the switch adjusts the power budget according to the
powered-device IEEE classification. If the powered device is a class 0 (class status unknown) or a
class 3, the switch budgets 15,400 mW for the device, regardless of the CDP-specific amount of power
needed. If the powered device reports a higher class than its CDP-specific consumption or does not
support power classification (defaults to class 0), the switch can power fewer devices because it uses the
IEEE class information to track the global power budget.
By using the power inline consumption wattage interface configuration command or the power inline
consumption default wattage global configuration command, you can override the default power
requirement specified by the IEEE classification. The difference between what is mandated by the IEEE
classification and what is actually needed by the device is reclaimed into the global power budget for use
by additional devices. You can then extend the switch power budget and use it more effectively.
Step 3 power inline {auto [max max-wattage] |
never | static [max max-wattage]}
Configure the PoE mode on the port. The keywords have these meanings:
• auto—Enable powered-device detection. If enough power is
available, automatically allocate power to the PoE port after device
detection. This is the default setting.
• (Optional) max max-wattage—Limit the power allowed on the port.
The range is 4000 to 30000 mW. If no value is specified, the
maximum is allowed.
• never—Disable device detection, and disable power to the port.
Note If a port has a Cisco powered device connected to it, do not use
the power inline never command to configure the port. A false
link-up can occur, placing the port into the error-disabled state.
• static—Enable powered-device detection. Pre-allocate (reserve)
power for a port before the switch discovers the powered device. The
switch reserves power for this port even when no device is connected
and guarantees that power will be provided upon device detection.
The switch allocates power to a port configured in static mode before it
allocates power to a port configured in auto mode.
Step 4 end Return to privileged EXEC mode.
Step 5 show power inline [interface-id |
module switch-number]
Display PoE status for a switch or a switch stack, for the specified
interface, or for a specified stack member.
The module switch-number keywords are supported only on Catalyst
3750-X switches.
Step 6 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose