!!PWRxFish-Final01.book Page 6 Tuesday, October 7, 2003 1:58 PM
General PoE Operation
How Does the Switch Prioritize Power Allocations?
The switch simul
taneously uses two priority methods:
■
The
priority class
method enables port PoE priority class assign
ments of
Low
(the default),
High
, and
Critical
.
■
The
port-number priority
method gives a lower-numbered port
priority over a higher-numbered port within the same configured
priority class.
Suppose, for example, that you configure PoE priority as shown in table 2.
Table 2.
Example of PoE Priority Operation
Port
Priority
Setting
Configuration Command
1
and Resulting Operation
25 - 48
Critical
This priority class always receives power. If there is not enough power to provision PDs on
all of the ports configured for this class, then no power goes to ports configured for High and
Low priority. If there is enough power to provision PDs on only some of the "Critical" ports,
then power is allocated to the "Critical" ports in ascending order, beginning with the lowest-
numbered port in the class, which, in this case, is port 25. For this example, the CLI command
to set ports to “Critical” is:
HPswitch(config)# interface e 25-48 power critical
9 - 12
High
This priority class receives power only if all PDs on ports with a Critical priority setting are
receiving full power. If there is not enough power to provision PDs on all ports with a High
priority, then no power goes to ports with a Low priority. If there is enough power to provision
PDs on only some of the "High" ports, then power is allocated to the "High" ports in ascending
order, beginning, in this example, with port 9, until all available power is in use. For this
example, the CLI command to set ports to “High” is:
HPswitch(config)# interface e 9-12 power high
1 - 8
Low
This priority class receives power only if all PDs on ports with High and Critical priority
settings are receiving power. If there is enough power to provision PDs on only some Low
priority ports, then power is allocated to the ports in ascending order, beginning with the
lowest-numbered port in the class (port 1, in this case), until all available power is in use. For
this example, the CLI command to set ports to “Low”
2
is:
HPswitch(config)# interface e 1-8 power low
13 - 24
- n/a -
For this example, PoE is disabled on these ports. The CLI command for this setting is:
HPswitch(config)# no interface e 13-24 power
1
For a listing of PoE configuration commands, with descriptions, refer to “Configuring PoE Operation” on page 7.
2
In the default PoE configuration, the ports are already set to the
low
priority. In this case, the command is not necessary.
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