Configuring a Microsoft Windows 2000 DHCP and DNS Server

Transcription

1 Configuring a Microsoft Windows 2000 DHCP and DNS Server White Paper Abstract This white paper sets out to describe the steps necessary to install a Brother printer into a Windows 2000 network that is using DHCP and DNS. However, if you are generally interested in how DHCP and DNS works, then this is a good starting point. Brother network ready printers can automatically receive an IP address from a Microsoft DHCP server and through the use of DNS, they can then be automatically registered with a DNS server. This can streamline the installation and maintenance of the printer in a Windows network. Last modified: January

2 Windows 2000 DHCP Server Overview With Windows 2000, Microsoft have enhanced the DHCP and DNS support capabilities found in Windows NT 4, to produce a more powerful IP address allocation and name resolution system. DHCP and DNS forms an integral part of any Active Directory installation. With Windows 2000, Dynamic DNS allows one DNS server to talk to another and change the DNS information automatically without having to manually edit files. Windows 2000 DHCP server integrates well into DNS, and devices that connect to the network, can be configured to automatically register themselves with a DNS server. This means that WINS based name resolution systems that were often found on Windows NT 4 systems can ultimately be replaced with DNS name resolution systems giving greater flexibility and more power to the user. The following documentation explains the steps necessary to configure a DHCP server onto a Windows 2000 system and have that system allocate IP addresses to the device. The second part of the document explains how the DHCP server can then be used to map the device into the DNS server for better name resolution. Brother has produced a wide variety of information on networking printing. Other documents that are relevant to this specific document are: For a complete list of network documentation, please visit the Brother web site at: Structure of this document This document is split into three sections: Section 1 Configuring DHCP for the first time - describes the steps necessary to configure a DHCP server. Section 2 Making a Reservation - describes how you can find a printer in the active directory as well as how to obtain the status of the printer using Windows 2000 and/or a web browser. Section 3 Making the device register itself with the Windows 2000 DNS server information on how to make the device register itself with a Windows 2000 DNS server. For more information on Windows 2000 and its capabilities, we recommend that you visit the Microsoft web site at

3 What is DHCP? DHCP (Dynamic Host Configuration Protocol) is a system where-by a computer, in this case a Windows 2000 computer, can allocate IP addresses to other computers on the network automatically. Typically in large networks, it can be difficult for the system administers to assign IP addresses to users In a large network with people joining and leaving the company, IP address allocation can be a headache. As people join the company new IP addresses are required and as people leave the company IP addresses are released and become free to other users. To get around this type of problem, companies like Microsoft have developed DHCP services that automatically allocate IP addresses to devices that are connected to the network. This means that when a PC or a printer is switched on, it will request an IP address from the DHCP server, if one is available, the DHCP server will allocate an IP address and then keep a track of it for future use. A good example of an organisation that would use a DHCP server is an Internet Service provider (ISP). These ISPs typically have many thousands of customers (in some cases millions) however, the ISP does not have unlimited modem connections for all of their customers to connect to. Because of this, they can be sure that if they have 100,000 customers, only 5000 of them may dial in and access the Internet at any one time. This means that instead of having to manage 100,000 IP addresses, the ISP simply builds a DHCP server that allocates 5000 IP addresses to people as they log on. This means that someone logging into the ISP one day, will typically receive a completely different IP address another day. By doing this, the ISP has an easier job and can control their network more easily. Just as an ISP would use DHCP for IP address allocation, many corporate networks will also use it for similar reasons. DHCP support is not new for Microsoft; it was also supported in previous versions of Windows. For example, Windows NT 4 also has good DHCP capabilities. As the theme of this document is Windows 2000, then information contained herein is based on the Windows 2000 implementation of DHCP. What is DNS? DNS (Dynamic Name Server) is a system that it widely used on the Internet. When we visit a web site such as DNS takes the name and maps it to an IP address. This is convenient for us as people are generally bad at remembering IP addresses, whereas, they are better at remembering names. For example, is someone says to you: goto you can remember it, but if someone says: goto , it is more difficult to remember. Even though the Internet uses the TCP/IP protocol and IP addresses, these numbers are hidden from us and instead we see a FQDN (Fully Qualified Domain Name) such as When we type in and hit RETURN on our web browser, our PCs contact a DNS server which converts the FQDN name that we entered into an IP address. This procedure is called name resolution and it simply means that we do not have to remember complicated IP addresses.

4 If you can browse the Internet through your PC, you can check to see that this is working by doing the following: Go to your DOS prompt and enter: PING you will see that you get an IP address back from the PING command, this is because a DNS server has converted the FQDN ( into an IP address. Then go back to your web browser and enter: where IP address is the number that you got back from the PING command. DNS is also useful for load balancing; a busy site like Microsoft.com will typically consist of several servers each of which can contain a duplicate of the other servers. This means that when one user enters on their web browser, they will connect to one server, however another using visiting the same company web site will connect to another server which contains a mirror copy of the data. By creating several servers with duplicate data, a web site can serve many more people than a single server.

5 Configuring DHCP for the first time When Windows 2000 is installed for the first time, the installation Wizard will prompt you to install Active Directory. Active Directory requires Microsoft s DNS server and also expects to use the DHCP services supplied with Windows If you have created a DHCP configuration prior to installing and configuring Active Directory, then your DHCP configuration settings will be lost. This means that you will have to re-configure everything. The following screen displays a DHCP server that has not been configured at all. The first thing that we must do is to allocate a server to become a DHCP server. To do this select Action and then click Add Server. Figure 1 Starting the DHCP server for the first time

6 Click the This server radio button and click OK. If you have other servers in your network that you wish to configure, click the Browse button and select another server. Figure 2 Selecting the Server Now that you have allocated the server which will act as the DHCP server, click the server name and then select Action followed by New Scope. Figure 3 DHCP server with no configuration details The New Scope Wizard will start. You can now optionally enter the Name and Description for the scope. Enter the information and click Next.

7 Figure 4 about to specify the start and end IP address information In the screen above you can see that you expected to enter a variety of different things: Start IP address: This is the first set of IP addresses that you wish to allocate. For example, if you wish to allocate IP addresses from to , you would enter: End IP address: This is the last IP address that you wish to allocate. Using the above example, we would enter if this is the last IP address that we wished to allocate. Length: This is to do with the subnet mask you use. Basically, if you use a subnet mask of then the length field will be 8. If you are using a subnet mask of then length field will be 16. If you are using a subnet mask of , the length will be 24. Subnet mask: The actual subnet mask value. Instead of click the length field, you can manually enter the value.

8 Figure 5 Specified the start and end IP address information along with the subnet mask With the above configuration we have configured the DHCP server to allocate IP addresses from the range through to We have also set the subnet mask so that each machine that receives an IP address will also receive a subnet mask of We can now optionally enter some exclusion IP addresses. Figure 6 The Add Exclusions configuration An exclusion is an IP address that could be reserved for something else. For example, imagine that we wished to use the IP address pool through to however we specifically wanted to keep some IP addresses free (maybe for laptop users, printers, etc.) we could enter an exclusion that protected those IP addresses. To exclude

9 an specific IP address, simply enter the IP address and then click Add. Study the screenshot below: Figure 7 Add exclusions wizard with IP addresses configured In the example above we have specified three things: Exclude the IP address and and also the IP addresses through to When you have finished entering the excluded IP addresses click the Next button. You are now prompted to specify how long the IP address should last for.

10 Figure 8 Setting the lease duration In the screenshot above you can see that the default IP address lease duration is 8 days. This means that when a device receives an IP address from the DHCP server, it will retain that IP address for 8 days. If you wish to change the lease duration, simply alter the time period and click Next when you are happy. After the lease duration you are given the option of specifying additional options.

11 Figure 9 About to activate the scope Additional options are things such as the IP address of a gateway, the IP address of a DNS server etc. Generally speaking when you configure a PC into a Windows 2000 network, or into a network where the connected PC will connect to the Internet, there is a good chance that you will want to specify these optional items. There are many optional items that you can specify, however, the wizard will only let you specify three things: The Gateway. The Gateway address is the address of the server that is used to contact other networks. Typically this is the IP address of a device like a router. Domain name and DNS server. This is the name of the DNS server that will handle the name resolution. DNS support has been greatly enhanced in Windows 2000 and if you intent to use Microsoft Active Directory technology, then you will must install a DNS server. WINS server. This is the IP address or NetBIOS name of the server that will handle name resolution. WINS (Windows Internet Naming Service) is now regarded as a legacy system (an old system), however, in order for Microsoft to be able to communicate with older Windows NT 4 systems, WINS support is still included.

12 Figure 10 Specifying the Router (Default Gateway) Enter the name of the default gateway (if applicable). The number you enter here will be used by the receiving device. It will be used to communicate with other networks that may exist in your environment. Generally speaking, if you are in a LAN (local area network) that is not connected to another LAN, then there is no need to specify the Default Gateway address.

13 Figure 11 DNS options Enter the name of the parent domain that you will use along with the server name (or IP address) of the DNS server. A client PC will then query the DNS server name whenever it tries to perform some kind of name resolution task, i.e., entering on a web browser, would make the client PC contact the DNS server that you specified and then locate the IP address for the IP address of Figure 12 WINS options To be compatible with Windows NT 3.51 and NT 4. Windows 2000 can also interact with WINS servers. This allows PCs and printers to use a NetBIOS name for name resolution.

14 Figure 13 About to activate the scope After completing all the above steps, the Wizard finally prompts you to activate the scope. Activating the scope essentially switches on all the options that you have specified. From this point onwards, any devices that are connected to your network that support the DHCP protocol, will receive the IP address information that you have configured. If you wish to activate it click Yes, I want to activate this scope now, if not select No, I will activate this scope later. We will assume that the configuration is OK, so we will activate the scope. You will now see a screen similar to the one below:

15 Figure 14 The DHCP server now running From the status column we can see that the scope is Active. This means that the server is ready to allocate IP addresses.

16 To test that the scope is working, configure a PC so that it receives an IP address automatically. Then re-boot the PC and the computer will contact the DHCP server for an IP address. If you have a Brother printer that has not been configured, switch the printer on and see what happens. If all goes well, the printer will contact the DHCP server and ask for an IP address just like a regular PC. Figure 15 TCP/IP properties of a Windows PC The screenshot above shows us a Windows 95/98 PC which has been configured to receive an IP address from a DHCP server. To see this screen select Start Settings Control Panel and then click the Network icon. If a PC is configured in this way, it will attempt to contact a DHCP server when powered on. Please note that Brother printers automatically default to AUTO IP address mode. This means that when powered up, they will query the network for a DHCP server, if one is found, the printer will request an IP address

17 To see if the DHCP server is allocating IP addresses, go to the Address Leases view. This will then display all the devices that have received an IP address from the DHCP server. Figure 16 Seeing devices that have been allocated IP addresses In the screenshot above, we can see that this particular server has allocated three IP addresses: to a device with the name brn_ to a device with the name gmob to a device with the name buk125w.

18 To see why those particular IP addresses were used take a look at the Address Pool view: Figure 17 Seeing the Address Pool information In Figure 16 we can see that the server has excluded the IP addresses through to , and This is why the DHCP server did not allocate the IP address DHCP is now configured in its most basic way. The remainder of this document explains some of the other options of DHCP server.

19 Making a Reservation So far we have randomly allocated IP addresses to devices that connect to the network. We say randomly, not because the numbers that we allocate actually random, but because we have no control over what device receives what IP address. For example, there many be instances when we wish to specially assign an IP address to a particular device. For example, if we had a network colour printer such as the Brother HL-2400CeN we could chose to allocate a specific IP address to this device. To do that we must establish the Ethernet address of the device that we wish to configure. Print out a configuration page to obtain the Ethernet address of the device. The Ethernet address will look something like this: <Ethernet Address> xx-xx-xx (where xx-xx-xx are a unique number) is the manufacturer code. If you see then you know that the device is a Brother device as this is the code allocated to Brother. Now that we know the Ethernet address, use this information to force the DHCP server to specifically allocate an IP address to this device. To do this, click on Reservations and then select New Reservation. Figure 18 About to make a reservation Now enter the name of the reservation and also enter the Ethernet address, also known as MAC (Ethernet address) address into the Mac Address field.

20 A correctly configured reservation would look like the following: Figure 19 Entering the reservation information Most of the above is logical, however, the one area that may cause some confusion is the Supported types option. Here we can specify one of three things: Both, DHCP only or BOOTP only. Windows 2000 allows you to configure these options, because as well as acting as a DHCP server, it is also able to allocate BOOTP IP addresses. BOOTP is the pre-cursor to DHCP; its job just like DHCP is to allocate IP addresses. However, BOOTP is more commonly found on Unix systems and unlike DHCP, a BOOTP configuration requires you to know the Ethernet (or MAC) address of each device before the server can allocate an IP address to it. To improve compatibility with Unix systems, Microsoft have also given Windows 2000 the option to allocate BOOTP IP addresses to a device. This effectively means that even though we are using the Windows 2000 DHCP Snap In. We are effectively making the DHCP server allocate BOOTP IP addresses. The supported types option in the above screenshot is simply allowing us to create a reservation for the Ethernet address that we have specified and allowing us to choose which IP address allocation system we wish to use. For example, if the device did not support the DHCP protocol, then we could select BOOTP and Windows 2000 would only try to use the BOOTP protocol for IP address allocation. Generally speaking, you would not alter this option. When the option is created you will see something like the one below:

21 Figure 20 The reservation is now configured Now we can see that a reservation has been put in place which means that the device that we specified, will contact the DHCP server and request the specific IP address that we allocated. Figure 21 Seeing the Address Leases In the above screen shot you can see that the device brn_313cfc has been allocated an IP address of

22 Making the device register itself with the Windows 2000 DNS server As we have already said, the Windows 2000 DHCP server has good integration with DNS. Any device that receives an IP address from the DHCP server should register itself with a Windows 2000 DNS server. This will allow you to easily name the devices in a more logical way. To configure the DHCP server does register the device with the DNS server do the following: Select the Scope that you wish to configure and then click the DNS tab. You will then see the following: Figure 22 The DNS tab properties In the above screenshot we can see that automatically a device that receives an IP address from the scope that we have configured will update the DNS server, only if the client requests it to do so. On a device like a printer, it will not request that its IP address is registered into the DNS server. This means that you should select the Always update DNS option. You should also consider selecting the Enable updates for DNS clients that do not support dynamic update. However, if you do not care about DNS name resolution from legacy PCs or from devices like printers, then ignore this option.

23 Figure 23 Configuring the DNS option so that devices always register in the DNS server In the above screenshot we have enabled the Enable update for DNS clients that do not support dynamic updates and also selected Always update DNS. This will guarantee that all devices will also be added to the DNS server.

24 You should also specify the DNS Domain name in the DHCP server. To do that select Scope Options and right click and select Configure Options. Now select option 015 DNS Domain Name and enter the name of your DNS server. Figure 24 Scope options DNS domain name In the above example, we have entered the value headquarters.test.brother.co.uk as this is the domain name of our DNS server. You must enter the DNS Domain name before the device that receives an IP address can register with the DNS server. If we now look at the DNS server, we can see if the device has registered itself with the Windows 2000 DNS server. Figure 25 Device has registered into the DNS server

25 The print server BRN_ has now registered itself on the DNS server. To check it, use the PING command using the DNS name instead of the IP address. Figure 26 Pinging the DNS name You can use this fully qualified domain name when managing the printer in a web browser. In the example below the user has entered a the DNS name of the printer, in the example below:

26 Disclaimer Brother reserve the right to change specifications without notice. Add trademarks are registered trademarks are the property of their respective companies. This information is provided as is without warranty of any kind. In no event shall Brother or its subsidiaries and suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages.