Setting up a DHCP server in Windows 2003

What is DHCP ?

The Dynamic Host Configuration Protocol (DHCP) is an auto configuration protocol used on IP networks. Computers that are connected to IP networks must be configured before they can communicate with other computers on the network. DHCP allows a computer to be configured automatically, eliminating the need for intervention by a network administrator. It also provides a central database for keeping track of computers that have been connected to the network. This prevents two computers from accidentally being configured with the same IP address.

There are two versions of DHCP, one for IPv4 and one for IPv6. While both versions bear the same name and perform much the same purpose, the details of the protocol for IPv4 and IPv6 are sufficiently different that they can be considered separate protocols.

In the absence of DHCP, hosts on an IP network must either use stateless address autoconfiguration to obtain their IP address, or must be configured manually. Because manual configuration is error-prone and time-consuming, it is not in common use. On IPv6 networks, stateless autoconfiguration and DHCP both have advantages, but on IPv4 networks stateless autoconfiguration is only useful for communication on the local subnet, and thus does not compete with DHCP.

Source - wikipedia.org

The above diagram diplays a simple structure consisting of a DHCP server and a number of client computers on a network.

The DHCP Server itself contains an IP Address Database which holds all the IP addresses available for distribution. If the client (a member of the network with a Windows 2000 Professional/XP operating system, for example) has "obtain an IP address automatically" enabled in TCP/IP settings, then it is able to receive an IP address from the DHCP server.

Setting Up DHCP

This will serve as a step-by-step guide on how to setup a DHCP server.

Installing the DHCP server is made quite easy in Windows 2003. By using the "Manage your server" wizard, you are able to enter the details you require and have the wizard set the basics for you. Open to "Manage your server" wizard, select the DHCP server option for the list of server roles and press Next. You will be asked to enter the name and description of your scope.

Scope: A scope is a collection of IP addresses for computers on a subnet that use DHCP.

The next window will ask you to define the range of addresses that the scope will distribute across the network and the subnet mask for the IP address. Enter the appropriate details and click next.

You are shown a window in which you must add any exclusions to the range of IP addresses you specified in the previous window. If for example, the IP address 10.0.0.150 is that of the company router then you won't want the DHCP server to be able to distribute that address as well. In this example I have excluded a range of IP addresses, 10.0.0.100 to 10.0.0.110, and a single address, 10.0.0.150. In this case, eleven IP's will be reserved and not distributed amongst the network clients.

It is now time to set the lease duration for how long a client can use an IP address assigned to it from this scope. It is recommended to add longer leases for a fixed network (in the office for example) and shorter leases for remote connections or laptop computers. In this example I have set a lease duration of twelve hours since the network clients would be a fixed desktop computer in a local office and the usual working time is eight hours.

You are given a choice of whether or not you wish to configure the DHCP options for the scope now or later. If you choose Yes then the upcoming screen shots will be of use to you. Choosing No will allow you to configure these options at a later stage.

The router, or gateway, IP address may be entered in next. The client computers will then know which router to use.

The last step is to activate the scope - just press next when you see the window below. The DHCP server will not work unless you do this.

The DHCP server has now been installed with the basic settings in place.

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Troubleshooting Network Connection Problems

Depending on how elaborate they are, home networks can be complicated. Unfortunately, because of this complexity, problems occasionally happen. Fortunately, you can usually solve these problems yourself. In most cases, finding the problem is a matter of going through a series of steps to eliminate potential issues one by one until you find the source of the problem. This article walks you through isolating your problem, troubleshooting the problem, and, if necessary, contacting the right organization for support.

If you are setting up your home network for the first time, refer to Set up a wired network or Set up a wireless network. The guidance in this article assumes that you were previously able to use your network, although the information here might be useful for troubleshooting setup problems, too.

How to isolate networking problems

People who work with networks think of them in terms of layers. These layers include the Internet, your modem and router, and the computer (or computers) on your network. To troubleshoot a problem effectively, you must first identify which network layer is causing the problem. The following diagram shows the different layers that might be the cause of a problem.

Although you can fix most problems yourself, if you can't fix a problem, it's helpful to know which layer is causing it so that you can contact the right organization for support.

To identify which layer is causing the problem

1.	Click Start, and then click Control Panel.

2. Click Network and Internet Connections.
 



3. Under or pick a Control Panel icon, click Network Connections.

4. In the Network Connections window, examine the status of your network adapter:

•	Connected. Your computer is properly connected to your modem, router, or wireless network, but there is a problem between your router and the Internet. Read Windows XP says your network adapter is connected.

•	Disabled. Someone has manually disabled the network adapter. To fix the problem, right-click the adapter, and then click Enable.

•	Unplugged. Your computer cannot detect the connection to your modem or router. Read Windows XP says your network adapter is unplugged.

•	Not connected. Your computer cannot connect to your wireless network. Read Troubleshooting Microsoft Windows XP-based wireless networks in the small office or home office.

•	Limited or no connectivity. Your computer is properly connected to your modem, router, or wireless network, but your router is misconfigured or there is a problem between your modem and the Internet. Read Windows XP says your network adapter has limited or no connectivity.

5. If your network adapter does not appear in the Network Connections window, it has not been properly installed. Uninstall the driver and network adapter as described in Troubleshoot device driver problems. Then reinstall the network adapter according to the manufacturer's instructions.

Windows XP says your network adapter is unplugged

If Microsoft Windows XP indicates that your network adapter is unplugged, it could be because of several different problems. Follow these steps to troubleshoot the problem. (You can stop following the steps if your network connection starts to work.)

1. Verify that both ends of the network cable are properly connected
2. If the cable is properly connected, verify that your modem and router are plugged in and turned on.
3. If you have more than one network port available in your router, plug the cable into a different port. If the network connection works, the original port on your router is faulty. However, you can continue to use the other ports.
4. Replace the network cable with a new cable. You might have a faulty network cable.
5. The network adapter on your computer might have failed. If possible, connect a different computer to the same network cable. If the connection works, the problem is with your network adapter. Contact your computer manufacturer for support, or install a new network adapter. If the new computer also fails to connect and you have already tried a new network cable, your network hardware (the device you connect the network cable to) has failed. Contact technical support for the network hardware, or replace it.

After following these steps, you should have identified the problem as your computer's network adapter, the network cable, or your network equipment, and then either replaced or repaired the failed device.

Windows XP says your network adapter has limited or no connectivity

If Windows XP says your network adapter has limited or no connectivity, it could be due to several different problems, including a failed Internet connection, a misconfigured router, or a misconfigured network adapter. Follow these steps to troubleshoot the problem. (You can stop following the steps if your network connection starts to work.)

1. In the Network Connections window, right-click your network adapter, and then click Repair. For detailed instructions
2. Unplug your modem. If you are unsure which device might be your modem, it is the device that is connected directly to your phone line (if you have DSL) or cable connection (if you have a cable modem). Wait one minute, and then plug your modem back in again.
3. If you have a router connected to your modem, unplug it. If you are unsure which device might be your router, look for the device that has at least two network cables: one that connects to your modem; and another that connects to your computer. You may also have a wireless router, which would be connected to your modem and would have one or more antennas. Wait one minute, and then plug your router back in again.
4. Restart your computer.
5. If your network adapter still shows "Limited or no connectivity" and you have customized your router's configuration, verify that the router has DHCP (Dynamic Host Configuration Protocol) enabled. Enable DHCP, and then restart your computer. DHCP automatically assigns an Internet Protocol (IP) address to your computer, which uniquely identifies your computer on your network. For instructions on how to enable DHCP for your router, refer to your router's documentation.
6. If you are using a router, unplug the network cable that connects your modem to your router, and connect your computer directly to your modem. Then restart your computer. If your computer connects properly after restarting, the problem is with your router. Contact your router manufacturer for support.
7. If your network adapter still indicates "Limited or no connectivity" when your computer is connected directly to your modem, contact your Internet service provider (ISP) for support. To speed up the troubleshooting process, describe the steps you have already taken, including restarting your modem, router, and computer, and connecting your computer directly to your modem. The "Limited or no connectivity" error message indicates that your computer is properly connected to your home network; however, the ISP's DHCP server is not assigning it an IP address. This problem could be caused by a failed DHCP server on the ISP's network, a failed modem, or a problem with your Internet connection. Alternatively, the ISP may require you to use a "static" IP address, which only its support staff can help you configure.

After following these steps, you should have identified the problem as your router, your modem, or your Internet connection, and then either reconfigured or repaired the failed component.

Windows XP says your network adapter is connected, but you can't reach the Internet

If you reached this section, your computer is probably connected to your home network properly, but there is a failure with your router, modem, or Internet connection. In this case:

1. First, verify that you can't reach the Internet. Start Microsoft Internet Explorer, and attempt to connect to the following Web sites: www.microsoft.com, www.msn.com, and www.windowsmarketplace.com. If any of the Web sites open correctly, your Internet connection is functioning properly. If all of the Web sites fail to open, continue following these steps.
2. Unplug your modem. If you are unsure which device might be your modem, it is the device that is connected directly to your phone line (if you have DSL) or cable connection (if you have a cable modem). Wait one minute, and then plug your modem back in again.
3. If you have a router connected to your modem, unplug it. If you are unsure which device might be your router, look for the device that is connected directly to your modem. Wait one minute, and then plug your router back in again.
4. Restart your computer.
5. If you have more than one computer on your network, turn the other computers off. Also, close any network applications that you might have open, including file sharing and peer-to-peer applications. These applications can consume so much bandwidth that they might prevent you from being able to browse the Web. Repeat step 1 to retest your Internet connection. If the connection works now, the problem is that one of your applications is consuming too much of your Internet bandwidth or attempting to connect to too many different computers. Close the application, or configure it to use less bandwidth or fewer connections.
6. If you have previously configured your computer with a static IP address (for example, to connect to your office network), you probably need an automatic IP address at home. Fortunately, you can configure Windows XP to use both by following the steps in Automatic configuration for multiple networks.
7. If you are using a router, unplug the network cable that connects your modem to your router, and connect your computer directly to your modem. Then restart your computer. If your computer connects properly after restarting, the problem is with your router. Contact your router manufacturer for support.
8. If possible, connect a different computer to your modem, and attempt to access the Internet. If the computer is able to access the Internet, you might have a problem with your Web browser. Contact your computer manufacturer for support.
9. Your modem or your Internet connection has failed. To resolve the problem, contact your ISP technical support. To speed up the troubleshooting process, describe the steps you have already taken, including restarting your modem, router, and computer, and connecting your computer directly to your modem.

After following these steps, you should have identified the problem as your router, modem, Internet connection, or Web browser, and then either reconfigured or repaired the failed component.