Learn about DHCP relay

We have learned a lot about the DHCP service and so on. We should also have some knowledge about DHCP relay. We all know that DHCP relay is also a very important part of the content, so for this part of content, we will explain it in detail this time. For more information, see the following.

Application Environment of DHCP relay

Early DHCP protocols are only applicable when the DHCP client and server are in the same subnet and cannot span network segments. Therefore, for Dynamic Host Configuration, you need to set up a DHCP server on all network segments, which is obviously not economical.

DHCP Relay is introduced to solve this problem: clients in the LAN can communicate with DHCP servers in other subnets through DHCP Relay, and finally obtain valid IP addresses.

In this way, DHCP clients on multiple networks can use the same DHCP server, which saves both costs and facilitates centralized management.

In general, DHCP relay can be a host or a router, as long as you start the DHCP relay agent service program on the device.

Interaction between DHCP relay and DHCP client and server

The interaction process between DHCP relay and DHCP client and server is as follows:

1. When the DHCP client starts and performs DHCP initialization, it broadcasts and configures request packets on the local network.

2. If the local network has a DHCP server, you can directly configure DHCP without DHCP relay.

3. if the local network does not have a DHCP server, after receiving the broadcast packet, the network device connected to the local network with the DHCP relay function, perform proper processing and forward it to the specified DHCP server on other networks.

4. the DHCP server configures the client based on the information provided by the client, and sends the configuration information to the client through DHCP relay to complete the dynamic configuration of the client.

In fact, there may be many such interactions from the beginning of configuration to the final completion of configuration.

It can be considered that DHCP relay provides a transparent transmission function for DHCP broadcast packets. It can transparently transmit broadcast packets from DHCP clients or servers to DHCP servers or clients in other network segments.

In the actual network environment, the DHCP relay function is generally implemented on a specific interface of the routing device. In this case, you need to configure the DHCP server address proxy for this interface.