Configure DHCP Servers

A Dynamic Host Configuration Protocol (DHCP) server provides network configuration parameters, such as IP addresses, to DHCP clients. You can configure a DHCP server on an interface to provide configuration parameters to DHCP clients on the attached network.

An IPv4 DHCP client uses a broadcast rather than a multicast address to reach the server. The DHCP client listens for messages on UDP port 68. The DHCP server listens for messages on UDP port 67. The DHCP server does not support BOOTP requests.

DHCP clients must be on the same network as the interface on which the server is enabled. There cannot be an intervening router between the server and client, although there can be a switch.

Caution

Do not configure a DHCP server on a network that already has a DHCP server operating on it. The two servers will conflict with each other, and the results will be unpredictable.

Procedure

Step 1

The section has two areas. Initially, the Configuration section shows the global parameters. The DHCP Servers area shows the interfaces on which you have configured a server, whether the server is enabled, and the address pool for the server.

Step 2

In the Configuration section, configure auto configuration and global settings.

DHCP auto configuration enables the DHCP server to provide DHCP clients with DNS server, domain name, and WINS server information obtained from a DHCP client that's running on the specified interface. Typically, you would use auto configuration if you're obtaining an address using DHCP on the outside interface, but you could choose any interface that obtains its address through DHCP. If you cannot use auto configuration, you can manually define the required options.

  1. Click the Enable Auto Configuration slider to On if you want to use auto configuration, and in the From Interface pull-down, select the interface that's obtaining its address through DHCP.

  2. If you do not enable auto configuration, or if you want to override any of the automatically configured settings, configure the following global options. These settings are sent to DHCP clients on all interfaces that host DHCP server.

    1. Primary WINS IP Address, Secondary WINS IP Address. The addresses of the Windows Internet Name Service (WINS) servers that clients should use for NetBIOS name resolution.

    2. Primary DNS IP Address, Secondary DNS IP Address. The addresses of the Domain Name System (DNS) servers that clients should use for domain name resolution. Click Apply Umbrella Settings if you want to populate the DNS IP address fields with Cisco Umbrella DNS servers. Clicking the button loads the appropriate IP addresses into the fields.

  3. Click Save.

Step 3

In the DHCP Servers section, either edit an existing server, or click New DHCP Server to add and configure a new server.

  1. Configure the server properties:

    1. Enable DHCP Server. Whether to enable the server. You can configure a server but keep it disabled until you are ready to use it.

    2. Interface. Select the interface on which you will provide DHCP addresses to clients. The interface must have a static IP address; you cannot be using DHCP to obtain the interface address if you want to run a DHCP server on the interface. For bridge groups, you configure the DHCP server on the Bridge Virtual Interface (BVI), not the member interfaces, and the server operates on all member interfaces. You cannot configure DHCP server on the Diagnostic interface, configure it on the Management interface instead, on the Device > System Settings > Management Interface page.

    3. Address Pool. Add the single IP address or an IP address range of a DHCP server. The range of IP addresses from lowest to highest that the server is allowed to provide to clients that request an address. The range of IP addresses must be on the same subnet as the selected interface and cannot include: the IP address of the interface itself, the broadcast address, or the subnet network address. Specify the start and end address for the pool, separated by a hyphen. For example, 10.100.10.12-10.100.10.250.

  2. Click OK.

Step 4

Click Save.

Step 5

Review and deploy the changes you made now, or wait and deploy multiple changes at once.