Dynamic Host Configuration Protocol (DHCP) is an invaluable service when you have a network larger than a handful of computers. It’s also a standard component of enterprise networks and sub networks. Microsoft Windows Server 2008’s built-in DHCP server allows Windows machines (and any other TCP/IP-based machines and devices) to obtain their IP addresses and network settingsautomatically, which can vastly simplify network configuration. In this document, we’ll discuss how to install and configure a DHCP server in Windows Server 2008, and we’ll explore some of the advanced features DHCP has to offer.
Create a plan
Before you configure your DHCP server, it is a good idea to have all your ducks in a row. Prepare and have all the necessary information up front before sitting down and configuring your server. For example, you may need to know:
- The scope of IP addresses that your server will manage (e.g., 192.168.1.50 to 192.168.1.200).
- Which machines require static IP addresses (i.e., those machines such as servers and routers that will not use DHCP to receive their IP addresses but will be set manually).
- Which network information you want to send out to DHCP clients when they get their IP addresses (e.g., the addresses for your default gateway, DNS servers, and WINS servers).
It is much easier to configure your DHCP server with this information in hand rather than scrambling for it at implementation time.
Installing DHCP
Installing a DHCP server in Windows 2008 is a snap. They created a very simple wizard that walks you through the entire process. Follow me on this journey.
To install a DHCP server from the Control Panel, follow these steps:
- From the Start menu, select | Control Panel | Administrative Tools | Server Manager.
- Expand and click Roles (Figure A).
- Choose Add Roles and follow the wizard by selecting the DHCP role (Figure B).
- A new DHCP wizard appears to help you configure a DHCP server.
Figure A
Server Manager
Figure B
Add Roles Wizard
In the previous release of Windows, a wizard did not appear to walk you through creating a DHCP server. Windows Server 2008 has really simplified this process by allowing you to configure a DHCP server in roughly seven steps. Of course, you can still manage your DHCP server from the DHCP Microsoft Management Console (MMC) snap-in or delete and create scopes on the fly.
Let’s continue on through the wizard. Your network cards and static IP addresses are automatically detected and you can choose how DHCP will service clients on different subnets, as shown inFigure C.
Figure C
Choose your static IP addresses to service DHCP clients
On the next window (Figure D), you can specify the applicable DNS server(s) to be used with DHCP when an address is assigned. Figure E displays where you would enter the applicable WINS servers if you require it on your network.
Figure D
Enter your DNS server IP address
Figure E
Enter your WINS server IP address
About scopes
When you create a scope, you must select the range of IP addresses and you must specify the appropriate scope options to include. These options are what we were referring to above when we mentioned that you can assign other network information to your clients at the time they are given an IP address.
There are two types of scope options: Global and Scope. Global options are propagated to all the scopes that you create on that DHCP server, while Scope options are only for the individual scope that you are working with.
For example, if you have different scopes for several different subnets and each subnet will have a different default gateway but will share the same DNS servers, you would want to set the DNS servers as a Global option while the default gateways would be set separately in each scope as a Scope option.
On the DHCP scope window, you will create your scope. Depending on the size of your network and the amount of users that will be assigned IP addresses, some thought must be given to the parameters of your scope selections. In my example (Figure F), I created a simple scope.
Figure F
Creating your scope
The subnet type dropdown allows you to choose wireless as well (Figure G). It defaults to 24 hours. If you want to activate the scope when the wizard is complete, click the Activate this scope checkbox. If you leave it empty, you must activate the scope in the DHCP Microsoft Management Console (MMC) snap-in.
Figure G
You can add multiple scopes before continuing the wizard
With Windows Server 2008, if you have a router (Figure H) that supports and is configured to take advantage of IPv6, you can enable this functionality on your network.
Figure H
Enable IPv6 stateless mode
Authorizing the DHCP server and activating scopes
In previous versions of Windows Server, you had to install and configure your DHCP server and then authorize it in the DHCP MMC snap-in. Authorizing your DHCP server allows you to prevent hackers from configuring rogue DHCP servers. In Windows Server 2008, you have the ability to either authorize the server in the Wizard or authorize it after the fact in the DHCP MMC-snap-in (Figure I).
Figure I
Authorizing your DHCP server
You are now ready to review (Figure J) and confirm your settings before applying your DHCP settings (Figure K).
Figure J
Reviewing your DHCP configuration before applying
Figure K
DHCP installation in progress
Once you have installed the DCHP server, you can manage it from the DHCP MMC snap-in (Figure O) located in Administrative tools. On this screen you can create additional exclusions and reservations.
Adding reservations
In addition to specifying exclusions, you can add reservations to your DHCP server. By adding a reservation, you ensure that a machine always receives the same IP address from the DHCP server.
- Right-click on Reservations and choose new reservation.
- Enter a friendly name for the reservation and the IP address you want to assign to the computer or device.
- Enter the MAC address of the computer or device. (For Windows machines, you can find the MAC address by running ipconfig/all from the command prompt of the machine.)
- Enter a description and then choose the following reservation type: DHCP, BOOTP (going across a router), or both, as shown in Figure L. Click Add.
Figure L
Adding a reservation
Adding exclusions
In addition to specifying reservations, you can add exclusions to your DHCP server (Figure M). By adding exclusions, you ensure that machines never receive a DHCP lease for that range of IP addresses. This is very useful to block IP addresses for your servers and routers.
Figure M
Adding an exclusion
In order to add Exclusions, right-click on Address Pools and choose New Exclusion Range as shown in Figure N and Figure O.
Figure N
IP address Exclusion range
Figure O
DCHP MMC snap-in
Troubleshooting DHCP
After configuring DHCP, the easiest way to troubleshoot it is to use Ipconfig from a command prompt. To view all TCP/IP information on a machine just type ipconfig/all. To release a DHCP lease, type ipconfig/release; to renew a lease, type ipconfig/renew.
