How Is Dhcp Option 82 Used - Dell Networking N4000 Series Configuration Manual

discover requests typically include options for the IP address (option 50),
subnet mask (option 1), default gateway (option 3), and DNS server (option
6). These options are predefined.
For options that are not predefined, you can enter the option code and specify
the data type along with the data that the switch should include in DHCP
offers. RFC2132 specifies many of the DHCP options. Additional options are
described in later RFCs.

How is DHCP Option 82 Used?

The Dell Networking Operating System (DNOS) supports insertion of
DHCP Option 82 information into DHCP messages relayed to DHCP
servers. The Dell Networking switch can be configured to insert either the
Circuit ID or the Remote ID or both. When enabled, the Circuit ID contains
the port identifier over which the DHCP request was received. The Remote
ID is configurable by the administrator on a per-switch basis.
Consider a network with multiple DHCP servers, where the administrator
wishes to serve addresses from a specific server based on the switch and port
to which the user station is connected. User traffic is served on VLAN 10 or
20.
The administrator globally enables DHCP relay and configures DHCP relay
on the end-user ports of each switch as follows:
console(config)#dhcp l2relay
console(config)#interface range gi1/0/1-24
console(config-if)#dhcp l2relay
console(config-if)#exit
Then, the administrator configures the remote-id and circuit-id:
console(config)#dhcp l2relay circuit-id vlan 10,20
console(config)# dhcp l2relay remote-id "Switch A" vlan 10,20
Finally, the administrator configures the uplink for DHCP relay and sets the
interface to trust Option 82 information received on the interface:
console(config)#dhcp l2relay
console(config)#interface range te1/0/1
console(config-if)#dhcp l2relay
console(config-if)#dhcp l2relay trust
console(config-if)#exit
1039
Configuring DHCP Server and Relay Settings