DELL N3000 User Manual

Configuring DHCP Server and Relay Settings

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.

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