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Catalyst 3750 Switch Command Reference
OL-8552-07
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
power inline
If the switch denies power to a powered device (the powered device requests more power through CDP
messages or if the IEEE class maximum is greater than the maximum wattage), the PoE port is in a
power-deny state. The switch generates a system message, and the Oper column in the show power
inline user EXEC command output shows power-deny.
Use the power inline static max max-wattage command to give a port high priority. The switch allocates
PoE to a port configured in static mode before allocating power to a port configured in auto mode. The
switch reserves power for the static port when it is configured rather than upon device discovery. The
switch reserves the power on a static port even when there is no connected device and whether or not the
port is in a shutdown or in a no shutdown state. The switch allocates the configured maximum wattage
to the port, and the amount is never adjusted through the IEEE class or by CDP messages from the
powered device. Because power is pre-allocated, any powered device that uses less than or equal to the
maximum wattage is guaranteed power when it is connected to a static port. However, if the powered
device IEEE class is greater than the maximum wattage, the switch does not supply power to it. If the
switch learns through CDP messages that the powered device needs more than the maximum wattage,
the powered device is shut down.
If the switch cannot pre-allocate power when a port is in static mode (for example, because the entire
power budget is already allocated to other auto or static ports), this message appears:
Command
rejected: power inline static: pwr not available
. The port configuration remains unchanged.
When you configure a port by using the power inline auto or the power inline static interface
configuration command, the port autonegotiates by using the configured speed and duplex settings. This
is necessary to determine the power requirements of the connected device (whether or not it is a powered
device). After the power requirements have been determined, the switch hardcodes the interface by using
the configured speed and duplex settings without resetting the interface.
When you configure a port by using the power inline never command, the port reverts to the configured
speed and duplex settings.
If a port has a Cisco powered device connected to it, you should not use the power inline never
command to configure the port. A false link-up can occur on the port, placing it into an error-disabled
state.
Examples This example shows how to enable detection of a powered device and to automatically power a PoE port:
Switch(config)# interface fastethernet1/0/2
Switch(config-if)# power inline auto
This example shows how to configure a PoE port to allow a Class 1 or a Class 2 powered device:
Switch(config)# interface gigabitethernet1/0/2
Switch(config-if)# power inline auto max 7000
This example shows how to disable powered-device detection and to not power a PoE port:
Switch(config)# interface gigabitethernet1/0/2
Switch(config-if)# power inline never
You can verify your settings by entering the show power inline user EXEC command.
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