DELL N3000 User Manual

Configuring L2 and L3 Relay Features

This chapter describes how to configure the L2 DHCP Relay, L3 DHCP 

Relay, and IP Helper features on Dell Networking series switches.
The topics covered in this chapter include:

• L2 and L3 Relay Overview
• Default L2/L3 Relay Values
• Configuring L2 and L3 Relay Features (Web)
• Configuring L2 and L3 Relay Features (CLI)
• Relay Agent Configuration Example

When a DHCP client and server are in the same IP subnet, they can directly 

connect to exchange IP address requests and replies. However, buying and 

maintaining a DHCP server on each subnet can be expensive and is often 

impractical. The relay features on the Dell Networking series switches can 

help enable communication between DHCP clients and DHCP servers that 

reside in different subnets. Configuring L3 DHCP relay also enables the 

bootstrap protocol (BOOTP) relay.

Network infrastructure devices can be used to relay packets between a DHCP 

client and server on different subnets. Such a device, an Layer 3 Relay agent, 

is often a router or L3 switch. The L3 relay agent must have an IP interface on 

the client subnets and, if it does not have an IP interface on the server’s 

subnet, it should be able to route traffic toward the server’s subnet.
The Dell Networking DHCP Relay Agent enables DHCP clients and servers 

to exchange DHCP messages across different subnets. The relay agent 

receives the requests from the clients, and checks the valid hops and 

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