3Com 3C17203 - SuperStack 3 Switch 4400, Руководство по внедрению

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Planning Power Budgets 115
have not had their power guaranteed. See “Configuring a Guaranteed
Power Plan” on page 116 .
2 Any device connected to a lower port number will take priority over a
device connected to a higher port number.
If the Switch needs to remove power from a device it will remove power
from the highest numbered port that has not been guaranteed power.
Devices that have been guaranteed power are not affected.
When the Switch is power cycled it will supply power first to guaranteed
ports that request power, then to the remaining ports, starting at the
lowest numbered port first.
Implementing a
Power Plan
If the total power required by your Power over Ethernet devices is less
than the Switch’s power budget then you can guarantee power to every
port.
If the total power required by your Power over Ethernet devices is more
than the Switch’s power budget then you will not be able to guarantee
power to all devices. If this is the case you may choose to:
■
Add additional Power over Ethernet switches — This will enable to
you guarantee power to each port on the Switch that supplies a
Power over Ethernet device. The remaining ports can be used to
supply networking to those devices that are powered by other means.
■
Prioritize Power over Ethernet devices — Since the Switch supplies
power to the lowest numbered port first, you should connect your
Power over Ethernet devices in order of importance, the most
important device being connected to the lowest numbered port. By
monitoring power consumption and checking if any devices have
been refused power you can decide whether additional Power over
Ethernet Switches will be required.
■
Guarantee power to critical devices — If you add an important Power
over Ethernet device to a high numbered port, you can still guarantee
power to this port (see
“Configuring a Guaranteed Power Plan”
below). The following rules apply to guaranteed power:
■
If you guarantee power to all active ports then no ports will be
disconnected or refused power. When additional Power over
Ethernet devices are added to your Switch, they will only be