User manual

C HAPTER 15 | Basic Administration Protocols
Power over Ethernet
– 224 –
ES-2000 Series
POWER OVER ETHERNET
The switch can provide DC power to a wide range of connected devices,
eliminating the need for an additional power source and cutting down on
the amount of cables attached to each device. Once configured to supply
power, an automatic detection process is initialized by the switch that is
authenticated by a PoE signature from the connected device. Detection and
authentication prevent damage to non-compliant devices (IEEE 802.3af or
802.3at).
The switch’s power management enables individual port power to be
controlled within the switch’s power budget. Port power can be
automatically turned on and off for connected devices, and a per-port
power priority can be set so that the switch never exceeds its power
budget. When a device is connected to a switch port, its power
requirements are detected by the switch before power is supplied. If the
power required by a device exceeds the power budget of the port or the
whole switch, power is not supplied.
Ports can be set to one of four power priority levels, critical, high, medium,
or low. To control the power supply within the switch’s budget, ports set at
critical to medium priority have power enabled in preference to those ports
set at low priority. For example, when a device connected to a port is set to
critical priority, the switch supplies the required power, if necessary by
denying power to ports set for a lower priority during bootup. If a device is
connected to a switch port and the switch detects that it requires more
than the power budget of the port, no power is supplied to the device (i.e.,
port power remains off).
If the power demand from devices connected to switch ports exceeds the
power budget set for the switch, the port power priority settings are used
to control the supplied power. For example:
◆ If a device is connected to a low-priority port and causes the switch to
exceed its budget, port power is not turned on.
◆ If a device is connected to a critical or high-priority port and would
cause the switch to exceed its power budget as determined during
booting up, power is provided to the port only if the switch can drop
power to one or more lower-priority ports and thereby remain within its
overall budget.
◆ If a device is connected to a port after the switch has finished booting
up and would cause the switch to exceed its budget, power will not be
provided to that port.
N OTE : Power is dropped from low-priority ports in sequence starting from
port number 1.
N OTE : For more information on using the PoE provided by this switch refer
to the Installation Guide.