Methods of Setting DHCP Options

The purpose of this article is to explain the differences between the four methods of setting Dynamic Host Configuration Protocol(DHCP) options. The four methods that can be used to set DHCP options are; Default, Global, Scope, and Client.

The following is a brief description of the four methods that can be used to set DHCP options:

Default

Setting a default DHCP option modifies the default value for one of the DHCP options. When a default value is set, the default value becomes the default that was set during administration rather than the DHCP default that was set during installation of DHCP. This method may be accessed through DHCP Manager, click "DHCP Options," then click "Defaults".

Global

When you set a global DHCP option, the option takes affect for all DHCP scopes defined on the selected DHCP server. Global DHCP options appear in DHCP Manager with a globe icon proceeding them. This method may be accessed through DHCP Manager, from the DHCP Options menu, click Global.

Scope

Setting a scope DHCP option will set the option only for the Selected scope on the Options Scope menu. DHCP options configured for a scope are displayed with a series of computer icons proceeding them in DHCP Manager. This method may be accessed through DHCP Manager, from the DHCP Options menu, click Scope.

Client

This method can be used to configure one or more of the DHCP options for a specific DHCP client. DHCP options can be set for a client only if the DHCP client has a reserved IP address(a Reservation). The only way to see if a DHCP option is set for a DHCP client is to view the properties of an active client lease through DHCP Manager. To do this, perform the following steps:

1. On the Scope menu, click Active Leases.
2. Select the individual client, click Properties, and then click Options.
   
   NOTE: If the Options button is not available, no reservation for the client exists.

NOTE: If a DHCP option is set by more than one method, precedence is in the following order:

1. Client Overrides...
2. Scope Overrides...
3. Global Overrides...
4. Default.