Dhcp Relayer - D-Link DFL-1600 User Manual

26.2. DHCP Relayer

279
26.2 DHCP Relayer
In DHCP implementation, the clients send requests to locate the DHCP
server(s) by broadcast messages. However, broadcasts are normally only
propagated on the local network. This means that the DHCP server and
client would always need to be in the same physical network area to be able
to communicate. In such a case, for a large Internet environment, it
requires a different server on every network, and the benefit of having one
centralized server configuration is greatly reduced. This problem is solved
by the use of DHCP relayer.
A DHCP relayer takes the place of the DHCP server in the local network to
act as the intermedium between the client and the remote DHCP server. It
intercepts requests from clients and relays them to the server. The server
then responds back to the relayer, which forwards the response to the
client. The DHCP relayers follow the BOOTP relay agent functionality and
retain the BOOTP message format and communication protocol, and
hence, they are often called BOOTP relay agents.
Example:
Configuring the firewall as a DHCP relayer
Configuration in this example allows clients on the VLAN interfaces to
obtain IP addresses from a DHCP server.
Before the following steps are taken, it is assumed that the firewall is
configured with VLAN interfaces that are going to use DHCP relaying, and
the IP address of the DHCP server has been defined in the address book
named as "ip-dhcp".
For information about VLAN configuration, please refer to 9.2.3, VLAN
Implementation. In this case, two VLAN interfaces named as "vlan1" and
"vlan2" are used.
The firewall will also install a route for the client when it has finalized the
DHCP process and obtained an IP.
D-Link Firewalls User's Guide