Reference Guide

800 | Power over Ethernet and Power over Ethernet Plus
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2. When you configure a port with power inline auto with the power limit option max_milliwatts, power is
only allocated after you connect a device to the port.
• If the maximum power for the device class is less than the power limit you specified, FTOS
allocates the required amount and returns the remaining amount to the budget.
• If there is not enough power in the budget, the configuration is maintained and the port waits for
power to become available.
• If the maximum power for the device class is more than than the power limit you specified, FTOS
does not allocate any power.
3. When you configure a port with
power inline static without the power limit option (max_milliwatts),
FTOS allocates 15.4W for PoE or 30.0W for PoE+ (subject to availability and priority) to the port
whether or not a device is connected.
4. When you configure a port with
power inline static with the power limit option (max_milliwatts), FTOS
allocates the specified number of Watts.
• If there is not enough power in the budget, the configuration is maintained and port waits for
power to become available.
• If the maximum power for the device class is more than than the power limit you specified, the
device is powered up until it consumes power less than the maximum allocated value. Otherwise,
it triggers overload condition (applies only to PoE+ ports).
Monitor the Power Budget
The power budget is the amount of power available from the installed PSUs minus the power required to
operate the chassis. Use the
show power inline (Figure 36-2) and show power detail (Figure 36-3)
commands to help you determine if power is available for additional PoE ports (1478.40 Watts are supplied
per C-Series Power Supply 1200W-AC); (1185.80W per Power Supply 1600W-AC in low-line mode,
1586.20W in high-line mode); max of 790W on S-Series with load-sharing external DC PSU).
Enabling PoE/PoE+ on more ports than is supported by the power budget produces one of these results:
• If the newly PoE/PoE+ -enabled port has a lower priority, then the command is accepted, but power is
not allocated to the port. In this case, the following message is displayed.
• If the newly PoE/PoE+ -enabled port has a higher priority, then the CLI is accepted, and power is
terminated on the lowest priority port in the chassis. If another power supply is added to the system at
a later time, both ports receive power.
• If all of the lower priority ports combined cannot meet the power requirements of the newly enabled
port, then the CLI is accepted, but power on the lower priority ports is not terminated, and no power is
supplied to the port.
Note: When a port is configured with power inline auto (with or without the max_milliwatts option) and the
PoE device is disconnected, the allocated power is returned to the power budget.
Message 1 Insufficient Power to Enable PoE/PoE+
%Warning: Insufficient power to enable. POE oper-status set to OFF for port <linecard/
portnumber>