Setting up a DHCP Scope

Access DHCP server click Start>Administrative Tools>DHCP. The green arrow next to the server indicates that the DHCP service is running. To create a new scope right-click on the server. Select New Scope. Click Next. Fill in Scope name and description, Click Next to continue. Next, specify the range of IP addresses available. Type the first IP address into the Start IP address box. Type the last available IP address into the End IP address box. Specify the subnet mask by either using the CIDR notation or the subnet mask. Click Next to continue.

Use the buttons below to navigate through the lesson

The Add Exclusions page allows you to specify an address or range of addresses to exclude from the scope. Click Next to continue.  The Lease Duration page allows you to change how long an IP address is leased to the client. The default of 8 days is good enough for most networks. Click on Next to continue. The Configure DHCP options page will appear, a scope can be configured to also give out additional information such as DNS and WINS addresses. To configure these options, ensure Yes is selected and click Next.
The Router page will appear. Type in the IP address of the router which will be given to the clients and click Add
The Router address of 11.1.0.151 has been added.
Click on Next to continue.
The DNS page allows DNS configuration information to be given automatically to clients. Type in the name of the parent domain into the Parent Domain box.

Type in the IP address of the DNS server into the IP address box. The DNS server’s name can also be specified.  Click on Add to add the address. Additional addresses can also be specified if need be. Click on Next to continue.  The WINS server address can also be specified. Type in the IP Address of the WINS server into the IP address box. The WINS server’s name can also be used. Click on Next to continue.

In order for clients to receive address leases, the scope will need to be activated. Ensure Yes is selected and click Next. Click on Finish to close the New Scope Wizard.  The scope is displayed in the DHCP management console.

Superscopes

Superscopes can group scopes into one manageable unit. It may contain several scopes each with a different range of addresses. All scopes will be treated as one, and addresses from any participating scopes will be given to clients on the network.

Superscopes are ideal if the available address pool for a currently active scope is nearly depleted, and more computers need to be added to the network. If the original scope already includes the maximum amount of hosts for its network ID then the only answer is to use another scope with another network ID to extend the address pool for the network.  If there are two or more separate network ID’s on the same physical network then a router will need to be configured. This is known as a multinetted network.

Creating a Superscope

The DHCP server “DNSTEST” currently has 2 active scopes. Both scopes have different network ID’s. To create a new superscope containing both scopes, right-click on the server. Select New Superscope.  The New Superscope Wizard will appear. Click on Next to continue. Type a name for the superscope into the Name box. Click on Next to continue.  The available scopes will be displayed. Highlight both Scopes. Both Scopes are selected. Click on Next to continue.  The summary page will appear. Click on Finish.

Both scopes are displayed. IP addresses from both scopes will be given out to clients on the network. A router will also need to be configured, since both scopes have different network ID’s.

Multicast Scopes

You can use a DHCP Server to provide the clients on your network with a multicast IP Address. Multicasts can send data simultaneously to a group of clients. Whereas a broadcast sends data to every client on the network, a multicast sends it only to clients who have a multicast IP address. The multicast address range uses an additional address class, Class D, which includes IP addresses that range from 224.0.0.0 to 239.255.255.255 for use in IP multicasting. Addresses in this class are used for multicasting only and not for regular DHCP scopes. Clients will receive a normal IP address as well as a multicast address.

A common use of multicast is for video conferencing and live broadcasts. Multicast scopes are supported through the use of Multicast Address Dynamic Client Allocation Protocol, the standard protocol for performing multicast address allocation.

Creating a Multicast Scope

To create a new multicast scope the DHCP console is used. Right-click on the server and select new multicast scope. The New Multicast Scope Wizard will appear. Click on Next to continue. Type in a name and description (optional) for the scope. Click on Next.

The valid range of IP addresses for a multicast (class D) scope begins at 224.0.0.0 and finishes at 239.255.255.255. Type the start and end IP addresses into the relevant boxes. The TTL value specifies how many routers the multicast will pass through before its blocked. Lowering the value to 1 will restrict traffic to the local segment. Type the value required into the TTL box. Click on Next to continue.

The Add Exclusions page will appear. From here you can exclude any IP addresses from the scope. Click on Next to continue. The Lease Duration page specifies how long the client will keep its multicast address. Click on Next to accept the default of 30 days. The scope will need to be activated in order for it to be any use. Click on Next to continue. Click on Finish to close the New Scope Wizard.  The new scope is displayed in the DHCP management console.

Configuring Scope Options

Once a scope has been setup and configured, additional options can be set which will be passed on to the clients. Most of the options are inconspicuous and may never be used. However, some options are useful. For example, the WINS node type can be configured using scope options. Options can also be configured for different types of clients, e.g. A laptop user and a desktop user.

DHCP Scope options are configured through the DHCP management console. Expand the DHCP server. Select Scope Options.  The list of options is displayed. A tick next to an option indicates that the option has been configured. Scroll down to view more options.

Click on the Advanced tab to view the advanced settings. The Vendor class allows you to configure options for different Vendor classes of machines, e.g. options specific to Windows 98 machines. Scroll-down to view the different vendor classes. This example shows that there are options that can be set primarily for Windows 2000 machines, and options that can be set for Windows 98 machines. The User class option can be used to configure different options for different clients. e.g. a client who is using remote access. Scroll the list down to view the different available class options. Server options act as defaults for all scopes. Server options can be overridden by defining the option in Scope Options.