Dell PowerConnect 5524P User Manual page 32

The relay agent information option (Option 82) in the DHCP protocol
enables a DHCP relay agent to send additional client information, upon
requesting an IP address.
Option 82 specifies the relaying switch's MAC address, the port identifier, and
the VLAN that forwarded the packet.
For more information, see "DHCP Relay" on page 577.
Identifying a Switch via LED
The switch provides the ability to turn on a LED (through the GUI interface)
on a specific unit or on all units in a stack for a specific length of time.
For more information, see Unit Identification (Location).
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Dell PowerConnect 55xx Systems User Guide