What is the DHCP Relay Agent?

The DHCP (for Dynamic Host Configuration Protocol) relay agent is a Bootstrap Protocol that relays DHCP messages between clients and servers for DHCP on different IP Networks. It can be a host or an IP router that “listens” to DHCP client messages being broadcast on the subnet and relays them to the configured DHCP server. The DHCP server would then send responses again using DHCP relay agent back to the DHCP client. The DHCP relay agent saves the administrator the agony of installing and running each DHCP server on each subnet. A DHCP server or a computer acting as a DHCP server is necessary for every IP network segment that has DHCP clients. These terms may sound a too wordy to some, so the definition of terms below may come as a relief.

DHCP-This is a client/server protocol that dynamically provides Internet Protocol (IP) addresses to hosts plus other configuration entries such as the Subway Mask and Default Gateway. Microsoft Windows Server 2003 OS has DHCP server service while Microsoft Windows 98, Millennium, NT, 2000, XP have DHCP client in their TCP/IP. One of the advantages of DHCP is that IP addresses are assigned from one central point minimizing the possibility of one IP being assigned to more than one computer which would create conflict.

* DHCP Server- This is a computer running the DHCP server service that has information as to which IP addresses are available as well as configuration information as defined by the administrator for DHCP.

* DHCP Client-This is a computer that receives its IP configuration information using DHCP.

Add a DHCP Relay agent.

In order to add DHCP relay agent, follow these instructions.

1) Open Routing and Remote Access. You can do that by typing this command prompt;

runas/user:[Domain/]UserName"mmc%windir%\system32\rrasmgmt.msc. Note that the user name must correspond to the administrators account.

2) On the console tree, click “General”. Follow this path: outing and Remote Access/server name/IP Routing/General

3) Right click on “General”, and then click on “new Routing Protocol”.

4) In a dialogue box called, “select Routing Protocol” click on “DHCP Relay Agent”.

5) Finish the procedure by clicking “Ok”.

If you want to configure the DHCP Relay Agent, follow these instructions:

1) Open the router and remote access as explained earlier.

2) On the console tree, open the DHCP relay client by following this path;

Routing and Remote Access/server name/IP Routing/DHCP Relay Agent.

1) Proceed to right click on “DHCP Relay Agent”, and then click on “properties”.

2) Go to the “General” tab and then select “Server address”, and then type the DHCP server address, and click “Ok”.

3) Repeat the previous step for each additional DHCP server that you add, and then click “Ok”.

If you wish to enable the DHCP Relay Agent on a routers interface, follow the following steps:

1) Proceed to open the router and remote access.

2) Once you are on the console tree, click on the DHCP Relay Agent.

3) Right click “DHCP Relay Agent” and select “New Interface”.

4) Select the interface that you want and then click on “Ok”. A dialogue box for DHCP relay Agent will appear, and on the “General” tab, you will verify that the Relay DHCP Packets check box has been, checked.

5) If it is deemed necessary, click the arrows on Hop-count threshold and Boot threshold (seconds) to modify the thresholds.