HP 2910AL - Manual (Page 264)

Power Over Ethernet (PoE+) Operation
PoE with LLDP
PoE with LLDP
Overview
The data link layer classification (DLC) for PoE provides more exact control
over the power requirement between a PSE and PD. The DLC works in
conjunction with the physical layer classification (PLC) and is mandatory for
any Type-2 PD that requires more than 12.95 watts of input power.
N o t e DLC is defined as part of the IEEE 802.3at standard.
The power negotiation between a PSE and a PD can be implemented at the
physical layer or at the data link layer. After the link is powered at the physical
layer, the PSE can use LLDP to repeatedly query the PD to discover the power
needs of the PD. Communication over the data link layer allows finer control
of power allotment, which makes it possible for the PSE to supply dynamically
the power levels needed by the PD. Using LLDP is optional for the PSE but
mandatory for a Type 2 PD that requires more than 12.95 watts of power.
If the power needed by the PD is not available, that port is shut off.
PoE Allocation
Enabling PoE-lldp-detect allows the data link layer to be used for power
negotiation.When a PD requests power on a PoE port, LLDP interacts with
PoE to see if there is enough power to fulfill the request. Power is set at the
level requested. If the PD goes into power-saving mode, the power supplied is
reduced; if the need for power increases, the amount supplied is increased.
PoE and LLDP interact to meet the current power demands.
Syntax: int <port-list> PoE-lldp-detect [enabled | disabled]
Allows the data link layer to be used for power negotiation
between a PD on a PoE port and LLDP.
Default: Disabled
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