DHCP Manager Scope Properties

• Microsoft Windows NT Workstation versions 3.5 and 3.51
• Microsoft Windows NT Server versions 3.5 and 3.51

The following information describes the general properties and maintenance activities performed on Microsoft DHCP scopes.

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The subnet identifiers and address pool make up the properties of scopes. You can change the properties of an existing scope by selecting the scope for which you want to change properties and then clicking Properties on the Scope menu. You can also double-click the scope to access its properties.

Modifying a Scope

After a scope has been created, you can extend the address range of the scope, but you cannot reduce it.

Removing a Scope

No leases can be active when a user wants to remove a scope. This task can be accomplished by deactivating the scope until all client leases expire or all client lease extension requests are denied. Once there are no more active leases contained in the scope, you can remove the scope by selecting the scope under DHCP Servers and choosing Delete on the Scope menu.

Add Reservations

You can configure DHCP so that a DHCP server always assigns the same IP address to a client. This is called a client reservation. This may be necessary because you may need to assign a DHCP client the same IP address every time it makes a request.

To configure a reservation, select the Scope under DHCP Servers and choose Add Reservations on the Scope menu. Type the appropriate IP address and the Unique Identifier/MAC address of the client. The unique identifier can be displayed by typing NET CONFIG RDR or IPCONFIG /ALL (WINIPCFG on Windows 95) from a command prompt.

One advantage of a reservation over an exclusion is that with a reservation, the clients can still be administered using the Active Leases option on the Scope menu. If you statically assign an address and exclude it from the scope, the client will not show up in the Active Leases list.

In addition, a reservation still requires that the client register with the DHCP server. This forces the client to accept the DHCP options that may be configured for the subnet. An exclusion will NOT receive DHCP options for that scope dynamically; they must be hardcoded on the client.

Active Leases

The Active Leases option allows a graphical display of current leased IPs as well as client reservation. If the computer symbol includes a phone, it is a lease owned by the RAS service (NDISWANx wrapper).

Although a client lease can be deleted from within this graphical display, the client may still receive the same address following an IPCONFIG /RENEW command because the client also has a copy of its address information locally. Until a client receives a different address or a negative acknowledgment (NACK) for a request to have the same address, it will ask for the same IP.