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What is DHCP Relay?

What is DHCP Relay?
DHCP is an acronym used for Dynamic Host Configuration Protocol. This protocol utilizes a relay structure to connect with the DHCP server. It serves as proxy that is utilized by the DHCP broadcast messages. These broadcast messages are important to be routed to different sectors in the subnet. For the configuration of DHCP relay, the address of the DHCP server is essential so messages or data can be relayed.

The purpose of having DHCP relay agent is to permit DHCP clients and servers be placed on numerous networks. It is not difficult to set up DHCP in a definite network segment. Messages in the DHCP network are IP broadcast and this means that all computers on the sector can respond. All it takes is a single scope on a single DHCP server.

DHCP messages flow easily on a single subnet on a network. However, things get a bit complex when there are many subnets on the network. The reason why things are complicated is that by default, DHCP broadcast messages do not cross router boundaries.

Fortunately, there are various ways or solution to deal with this problem. If the network is composed of just a few segments, placing DHCP server for every segment would do the trick. However, this solution is not recommended for large organizations. Putting up many DHCP servers will increase the expense of the company.

For organizations that are large and the network in use is a multi-segment, relays must be utilized. The trick is not to dedicate one DHCP server of each segment. Rather, put the machines in central locations. This will help save on cost instead of dedicating of 1:1 ratio for DHCP server on every segment. However, the problem is how to allow DHCP broadcast messages to pass the router interfaces.

To make DHCP broadcast messages intersect the router boundaries, a little configuration must be performed. Routers are designed so that it can go under configuration to relay DHCP/BOOTP messages on a selective manner. This configuration is also known as BOOTP relay.

Configurations may be a bit confusing especially the BOOTP concept. On the other hand, it can even get more perplexing when BOOTP forwarding comes into the scene. The BOOTP relay and BOOTP forwarding are two different concepts.

BOOTP forwarding is considered simpler. This is because there is no need for any distinctive processing to pass messages from one interface to another. On the other hand, BOOTP relaying is a little more complex. This concept needs changes or configuration to the primary packet.

There are routers that have no capability for a BOOTP Relay. To resolve this problem, a computer is set up on segments with DHCP clients. This will serve as the replacement for the BOOTP relay agent not supported by the router.
Oftentimes the terminologies make someone confused. As a tip, it is best to be familiar with the terminologies and their exact meanings. First, DHCP/BOOTP Relay agent is different from a Router that is utilized or acts as BOOTP forwarder. Forwarders are only capable of passing the broadcast message across router interfaces. On the other hand, DHCP relay does not just forward broadcasting message but it changes DHCP message before it forwards the message to a particular DHCP server.

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Posted by Jodel X on Feb 4th, 2011 and filed under Computer. You can follow any responses to this entry through the RSS 2.0. You can leave a response via following comment form or trackback to this entry from your site