Example: Simple DHCP subnet

In this example, the System i model acts as a DHCP server for the 10.1.1.0 IP subnet. It is connected to the LAN with its 10.1.1.1 interface.

With so few PC clients, administrators can easily type the information that is related to each PC's IP address and maintain this information. (They only need to visit four PCs in this case.) Now imagine that the four PCs become 200 PCs. Setting up each PC's IP information now becomes a time-consuming task that might result in accuracy errors too. DHCP can simplify the process of assigning IP information to clients. If the subnet 10.1.1.0 has hundreds of clients, an administrator only needs to create a single DHCP policy on the system. This policy distributes IP information to each client.

When PC clients send out their DHCPDISCOVER signals, the server responds with the appropriate IP information. In this example, the company also has a LAN-based printer that obtains its IP information from the DHCP server. But because PC clients depend on the printer's IP address remaining the same, the network administrator must account for that in the DHCP policy. One solution is to assign a constant IP address to the printer. You can use the DHCP server to define a client, like the LAN printer, in the DHCP policy by its MAC address. In the DHCP client definition, you can then assign specific values, such as IP addresses and router addresses, to the intended client.

For a client to communicate with a TCP/IP network, it requires at least an IP address and subnet mask. The clients will get their IP address from the DHCP server, and the DHCP server passes additional configuration information (for example, their subnet mask) using the configuration options.

Planning the DHCP setup for a simple LAN