Configuring DHCP Options
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
DHCP uses options to pass additional IP settings to DHCP clients on a network. Examples of DHCP options include:
The default gateway IP address
The DNS server IP address
The DNS domain name
You can configure DHCP options for specific values and enable them for assignment and distribution to DHCP clients based on server, scope, class, or reserved client levels. For example, you can enable the vendor class option Release on Shutdown for any laptops on your network to allow IP addresses assigned to mobile clients to be reincorporated into the address pool more quickly.
You can configure options for an entire server, a scope, or for a single reserved client. The most specific options (reserved client) take precedence over the least specific options (server). Values configured manually on a client override any DHCP options of any type and of any level.
Using the New Scope Wizard, you can configure some scope-level options, including router (default gateway), domain name, DNS servers, and WINS servers. You can also configure options at the server, scope, and reserved-client levels in the DHCP snap-in.
To configure server-level options
In the DHCP snap-in, expand the server for which you want to configure options.
Right-click Server Options, and then click ConfigureOptions.
In the Server Options dialog box, select the options you want to configure.
In the Data Entry section of the Server Options dialog box, type the option parameters, and then click OK.
To configure scope-level options
In the DHCP snap-in, expand the scope for which you want to configure options.
Right-click Scope Options, and then click Configure Options.
In the Scope Options dialog box, select the options you want to configure.
In the Data Entry section of the Scope Options dialog box, type the option parameters, and then click OK.
To configure options for a reserved client
In the DHCP snap-in, expand the scope that holds the reservation for which you want to configure options, and then expand Reservations.
Right-click the reservation for which you want to configure options, and then click Configure Options.
In the Reservation Options dialog box, select the options you want to configure.
In the Data Entry section of the Reservation Options dialog box, type the option parameters, and then click OK.
For more information about configuring reservations, see "Creating Reservations" later in this chapter.
Many option types are predefined in Windows Server 2003 DHCP. Other standard DHCP option types can be added as needed to support DHCP client software that recognizes or requires them. Windows Server 2003 DHCP supports all DHCP options, including those defined in RFC 2132, although most DHCP clients use or support only a small subset of the available option types.
In general, use the following guidelines when configuring DHCP options for clients on your network:
Add or define new, custom option types only if you have new software or applications that require a nonstandard DHCP option.
If your network is large, be conservative and selective when assigning global options. These options apply to all clients of a DHCP server, unless more specific options are specified.
Use scope-level options for most options that clients are assigned. Setting options at the scope level allows you to take scope-related differences into account, such as different client needs or the use of a different DNS server from other scopes in the network.
Use class-level options if you have a large network or diverse groups of clients that are able to support membership in option classes.
Use reserved client options only for clients that have special requirements, for example, if your intranet has a DNS server that performs forwarding for resolving Internet DNS names not authoritatively managed on your network. In this case, you need to add the IP address of an external DNS server on your DNS server computer. You can configure your DNS server as a reserved client in DHCP and set this address as another reserved client option.