Hello, everyone!
Today, I will continue to explain the DHCP protocol. In this last article, I will explain DHCP relay principles.
If there are several different and distant LAN networks, it is very expensive to have a DHCP server in each network. That is the reason why this principle was developed. It allows the existence of a single DHCP server that can assign network configuration parameters to a large number of DHCP clients from different LANs. All you need is a DHCP relay, which can be a cheaper device than a DHCP server.
In this way, I talk about three different devices:
DHCP server - one device for multiple DHCP clients from different LAN networks. It assigns network configuration parameters.
DHCP relay agent - a device that must be in every network where DHCP clients are located. DHCP clients communicate with the DHCP server through this device. This device is configured to forward DHCP messages.
DHCP client - devices that require network configuration parameters.
In the next figure, we can see DHCP clients in LAN network A and DHCP server is in network B.
Fig. 1. DHCP relay principles
DHCP clients require network configuration parameters (network A). To enable these network configuration parameters from another network (network B), it is necessary that there is a DHCP relay in their network (network A).
A DHCP relay can be a server, OLT, or router. And we have to configure this device to work as a DHCP relay. For PON technology, we usually use OLT for DHCP relay. In the next article, I will show and describe how to set up OLT as a DHCP relay. We have to configure the DHCP relay that can forward DHCP messages between the DHCP clients and the DHCP server.
Figure 2. DHCP relay process
As we can see in figure 2, communication between DHCP clients and the DHCP server is over the DHCP relay. The DHCP client does not know where the DHCP server is. DHCP client sends standard DHCP messages to get network configuration parameters. Messages exchanged between a DHCP relay and a DHCP server are exclusively unicast messages because the DHCP relay knows the location of the DHCP server.
Thank you!
For more information, please click:
