DHCP Configuration Overview

Topics on this page: What is DHCP? | Why use DHCP? | DHCP Modes | Setting the DHCP Mode

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You can configure your network and ADSL/Ethernet router to use the Dynamic Host Configuration Protocol (DHCP). This help topic provides an overview of DHCP and instructions for implementing it on your network.

See Configuring DHCP Server and Configuring DHCP Relay for specific instructions on setting up these services.  

What is DHCP?

DHCP is a protocol that enables network administrators to centrally manage the assignment and distribution of IP information to computers on a network.

When you enable DHCP on a network, you allow a device - such as your ADSL/Ethernet router or a router located with your ISP - to assign temporary IP addresses to your computers whenever they connect to your network. The assigning device is called a DHCP server, and the receiving device is a DHCP client.

Your may have already configured each LAN PC with an IP address, or you may have specified that each will receive IP information dynamically (automatically). If you chose to have the information assigned dynamically, then you configured your PCs to accept IP addresses assigned from a DHCP server such as the ADSL/Ethernet router.

The DHCP server draws from a defined pool of IP addresses and "leases" them for a specified amount of time to your computers when they connect to the network. It monitors, collects, and redistributes the addresses as needed.

On a DHCP-enabled network, the IP information is assigned dynamically rather than statically. A DHCP client can be assigned a different address from the pool each time it reconnects to the network.

Why Use DHCP?

DHCP allows you to manage and distribute IP addresses throughout your network from a central computer. Without DHCP, you would have to configure each computer separately with IP addresses and related information. DHCP is commonly used with large networks and those that are frequently expanded or otherwise updated.

DHCP Modes

The device can be configured as a DHCP server, relay agent, or client.

• If you configure the device as a DHCP server, it will maintain the pool of addresses and distribute them to your LAN computers. If the pool of addresses includes private IP addresses, you must also configure the Network Address Translation service, so that the private addresses can be translated to your public IP address on the Internet. Both DHCP server and NAT are enabled in the default configuration.
• If your ISP performs the DHCP server function for your network, then you can configure your device as a DHCP relay agent. When a computer logs onto the network, the ADSL/Ethernet router contacts your ISP for the necessary IP information, which it relays back to the computer.
• If you have another PC or device on your network already performing the DHCP server function, then you can configure the device's LAN port to be a DHCP client of that server (as are your PCs). This configuration is described in Configuring the LAN and USB Interfaces.

You can input settings for both DHCP server and DHCP relay mode, and then activate either mode at any time. Deactivated settings are retained for your future use.

Setting the DHCP Mode

You should set the DHCP mode only after you have configured DHCP relay or DHCP server settings. See Configuring DHCP Server and Configuring DHCP Relay for additional instructions.

Follow these instructions to set the DHCP mode:

1. If the DHCP Mode page is not already displaying, click  the Advanced Setup button, and then click the DHCP button. 
2. From the DHCP Mode drop-down list, choose DHCP Server, DHCP Relay, or None.

If you choose none, your LAN computers must be configured with static IP addresses.

3. Click Save Changes.