This document provides instructions for installing the DHCP Server service and configuring DHCP scopes and superscopes on a Windows server. It describes installing the DHCP service, configuring DHCP scopes to define IP address ranges and exclusions, creating superscopes to group multiple scopes, and configuring DHCP options like the TFTP server address. It also covers enabling DHCP on clients and some additional DHCP configuration settings.

1. Install DHCP Server Service,
DHCP Scopes & Superscopes
Jocelyn Tanner

2. Installing the DHCP Server Service
Prior to installing the DHCP service, you must log on as administrator from
the primary domain controller. To install the DHCP Server service, follow
these steps:
1. Run Control Panel and choose Network.
2. Choose Add Software.
3. In the Add Network Software dialog box, select TCP/IP Protocol And
Related Components, and then choose Continue.
The Windows NT TCP/IP Installation Options dialog box appears,
displaying the TCP/IP components available to be installed.
4. Select DHCP Server Service, and then choose Continue.

3. Installing the DHCP Server Service
• The Windows NT setup box appears, prompting you for
the full path of the Windows NT distribution files.
NOTE: You may be prompted with the following
message:
At least one of your adapters has automatic DHCP
configuration enabled. In order to correctly install the
DHCP server, setup will disable automatic DHCP
configuration. Are you sure you want to install the
DHCP Server?
Choose Continue.

4. Installing the DHCP Server Service
5. Type the path to the location of Windows NT Server distribution files, and
choose Continue.
If you install from compact disc, the path is under the I386 directory.
The TCP/IP configuration Box appears.
6. Enter the static IP address of the DHCP Server as well as the subnet mask and the
default gateway. If you use Windows Internet Name Service (WINS), add the
primary and secondary WINS addresses here.
The appropriate files are copied to your server, and then the Network Settings
dialog box appears.
7. Choose OK.
A Network Settings Change dialog box appears, indicating that the system must
be restarted to initialize the new configuration.

5. Installing the DHCP Server Service
8. Save any unsaved work in other windows and
choose Restart Now to restart Windows NT
Server.
9. Log on as Administrator.

6. Configuring a DHCP Scope
• Be sure to install and initialize the DHCP
Server before completing the next step.
To configure the DHCP scope, you must log on
as administrator. Configuring the DHCP scope
supplies the DHCP client with the range of IP
addresses from which the server draws from
and a subnet mask to be assigned to clients.

7. Configuring a DHCP Scope
• The DHCP Server provides:
Default gateway address
• Domain Name
• Service server addresses
• WINS server addresses
• NETBIOS name resolution type.
• Option 150 (TFTP servers for VoIP/VoSIP)

8. Configuring a DHCP Scope
1. From the Network Administration group, start DHCP
Manager.
The DHCP Manager window appears.
2. Under DHCP Servers, select *Local Machine*
Local Machine indicates that you are configuring the
local DHCP server, and not a remote DHCP server.
3. From the Scope menu, choose Create.
The Create Scope dialog box appears.

9. Configuring a DHCP Scope
4. Complete the scope configuration.
The DHCP server cannot be a DHCP client. It
must have a static IP address, subnet mask,
and default gateway address. You also have
the option of assigning an exclusion range or
specific excluded addresses as well as lease
duration and a name.
5. Choose OK when done.

10. Configuring a DHCP Scope
6. Choose Yes to activate the scope.
The DHCP Manager window appears with the
new scope added. Notice the yellow light
bulb next to the IP address. This indicates an
active scope.
7. Close the DHCP Manager.

11. Enabling DHCP at the Client
• To enable DHCP on a Windows for Workgroups
client if TCP/IP is not installed yet:
Use Network Setup to install the MS TCP/IP-32
3.11 protocol.
• In the MS TCP/IP Configuration dialog box, select
the Enable Automatic DHCP Configuration check
box, and choose Continue.
• Restart the computer to initialize TCP/IP using
DHCP.

12. What is a DHCP Scope?
• A DHCP scope is an administrative grouping of
computers running the DHCP Client service. You create
a scope for each subnet on the network to define
parameters for that subnet.
Each scope has the following properties:
1. A unique subnet mask to determine the subnet
related to a given IP address.
2. A scope name assigned by the administrator when the
scope is created.
3. Lease duration values to be assigned to DHCP clients
with dynamic addresses.

13. Using the DHCP Manager to
Create, Manage or Remove scopes
• The DHCP database file (Dhcp.mdb) is a JET
database that cannot be read by Microsoft Access
or other application editors.
To create a new DHCP scope, select the server in
the DHCP Manager window, and on the Scope
menu, click Create.
A pop-up window is displayed requiring all
necessary information to configure the DHCP
Server. To configure the new scope, type the
appropriate information into the following fields:

14. IP Address Pool
• IP Address Pool
Field Description
------------------------------------------------------------------------------------
Start address -- Specifies the first IP address of the scope for the
clients
End address -- Specifies the last IP address of the scope for the
clients
Subnet mask -- Specifies the subnet mask for the client subnet

15. Exclusion Range
• By specifying addresses to be excluded from a range,
DHCP Manager will not lease these addresses to
requesting clients. An example of this is a UNIX Tower
or similar machine that cannot be reconfigured with a
static IP address outside of the intended/defined scope
(for example, a corporate DNS).
To implement several address scopes within one
subnet on a single DHCP server, create one continuous
IP address range that includes all available addresses
within the subnet. Then, exclude necessary addresses
or ranges from within the defined scope.

16. Example of Exclusion Range
• Defined scope: 192.192.192.1 through 192.192.192.200
• Excluded: 192.192.192.5 and 192.192.192.10 through
192.192.192.50
• Available addresses: 192.192.192.1 through
192.192.192.4, 192.192.192.6 through 192.192.192.9, and
192.192.192.51 through 192.192.192.200

17. Lease Duration
Lease Duration Unlimited
• This option specifies that the DHCP lease
assigned to a client will never expire. This is not a
recommended option and should be substituted
through the use of client reservations.
Lease Duration Limited to
• The number of days, hours, and minutes that a
DHCP client lease is available before it must be
renewed.

18. Name & Comment
Name
• The scope name is the name that describes
this subnet and is displayed after the IP
address in DHCP Manager. The name can
include any combination of letters, numbers,
hyphens, underscores, or blank characters.
Comment
• This is an optional field.

19. Configuring Superscopes
• The enhanced DHCP server allows the administrator to create different
scopes (ranges of IP addresses), and then to group those scopes together
into a superscope.
• To create a superscope, complete the following steps:
1. Create each of the scopes using DHCP Manager. Assign global and scope
properties as desired. Be sure to enable each scope.
2. In DHCP Manager, select the DHCP server. Click Scope, and then click
Superscopes.
3. Click Create Superscope, supply a name for the superscope, and then
click OK.

20. DHCP Option 150 (TFTP servers)
Add the TFTP Option to the Scope
• Cisco IP Phones expect the DHCP server to
also provide the IP address of the TFTP server.
By default, the TFTP option is not available in
a newly defined DHCP scope. Complete these
steps in order to add the TFTP option to the
scope.

21. DHCP Option 150 (TFTP servers)
1. Right-click the server and select Set
Predefined Options, then click Add

22. DHCP Option 150 (TFTP servers)
2. Enter the Name as TFTP Server IP Address, Data Type is IP Address,
Code is 150, and Description is TFTP Server IP Address for CallManager
Devices.

23. DHCP Option 150 (TFTP servers)
3. Click OK and then Edit Array. Enter the IP address(es) for TFTP server(s)
that are normally housed on the Cisco CallManager systems.

24. DHCP Option 150 (TFTP servers)
4. Click OK twice in order to complete the creation of Option 150. Under the new
Cisco CallManager DHCP Scope you created is a field labeled quot;Scope Optionsquot;. If
you right-click Scope Options and select Configure Options, you can select Option
150 as an option to hand out to Devices.

25. DHCP Option 150 (TFTP servers)
5. Click Apply and OK in order to see that the scope now has Option 150.
6. Right-click the Scope and select Activate in order to activate the Scope.

26. Configuring Superscopes
4. Add the appropriate scopes from the Available Scopes
list to the Child Sub-Scopes list.
When finished, the Child Scopes should be listed from
top to bottom in the order that you want addresses to
be used from them.
NOTE: The order that you add the Child Sub-Scopes is
of no consequence. DHCP Manager will sort them in
ascending order.
5. Click OK.

27. Configuring Superscopes
6. If the DHCP server is configured with the
IgnorebroadcastFlag DHCP Registry value set to 0, and
if the Superscope is on a subnet that is directly
attached to the server (that is, not being reached via a
DHCP relay agent), then each of the logical subnets
must be directly reachable by the DHCP server.
This means that there must be a local route to each
logical subnet. The easiest way to accomplish this is to
add an IP address to the NIC on the local server for
each of the logical subnets that it is attached to.

28. IgnorebroadcastFlag DHCP Registry
Information
• Versions of the DHCP server prior to Windows NT 4.0 ignored the
broadcast flag in client DHCP packets, and broadcast all replies.
Version 4.0 of the DHCP server supports unicasting via the following
registry parameter:
•
HKEY_LOCAL_MACHINE CurrentControlSet Services DHCPServer
Parameters IgnoreBroadcastFlag Parameter Type: REG_DWORD
Default: 1
• Description: If set to 1, the broadcast flag in client requests is
ignored, and all DHCP packets are broadcast from the server. If set
to 0, the behavior (whether to broadcast or not) is controlled by the
broadcast flag in the client request that is being responded to.
• The Networks.wri file also contains a description of this parameter.

29. Questions!