ProSafe 7000 Managed Switch Software Administration Manual, Release 8.0.3
27-1
DHCP L2 Relay
v1.0, June 2010
Chapter
27 DHCP L2 Relay
DHCP Relay Agents eliminate the necessity of having a DHCP server on each physical network. Relay
Agents populate the
giaddr
field and also append the
Relay Agent Information
option to the DHCP
messages. DHCP servers use this option for IP address and other parameter assignment policies. These
DHCP Relay Agents are typically an IP routing aware device and are referred as Layer 3 Relay Agents.
In some network configurations, there is a need for Layer 2 devices to append the Relay Agent Information
option as they are closer to the end hosts. These Layer 2 devices are typically operating only as bridges for
the network and may not have an IPv4 address on the network in question. Lacking a valid IPv4 source
address, they cannot relay packets directly to a DHCP server located on another network. These Layer 2
devices append the Relay Agent Information option and broadcast the DHCP message. This chapter
provides information about where a Layer 2 Relay Agent fits in and how it is used.
DHCP Server #1
Host #1
Host #2
Layer 2 Switch #1
1/0/4
1/0/5
1/0/6
Figure
27-1
