Lesson 4: Resolving Name Resolution Issues


Name resolution is the process that allows network and Internet users to access resources by their names instead of their IP addresses. Names used might be (among other things) computer names, server names, printer names, or fully qualified domain names (FQDNs). Without name resolution, users would be forced to remember the IP addresses of each resource on the network or on the Internet. Thus, name resolution makes accessing resources much simpler. When problems occur with accessing network resources, often the solution involves troubleshooting these components.

  • After this lesson, you will be able to

  • Understand and resolve basic issues related to the Domain Name System.

  • Understand and resolve basic issues related to Windows Internet Naming Service.

  • Understand and resolve basic issues related to HOSTS files.

  • Understand and resolve basic issues related to LMHOSTS files.

  • Estimated lesson time: 15 minutes

Understanding DNS Issues

DNS servers resolve the names of network resources to their respective IP addresses. In a LAN, an administrator installs a DNS server and configures the information regarding the IP addresses of resources on the network. When something is wrong with the DNS configuration on a computer or the DNS server on a network, users will not be able to resolve computer names or FQDNs to their IP addresses, and connectivity to those resources will fail.

If you believe (because of results of ping, ipconfig /all, tracert, or other command-line tests) that an incorrect DNS configuration is preventing a user or users from resolving names to IP addresses, and you have verified the IP address of the DNS server and that the server is online, you should check the DNS settings on the local computer. You can view and reconfigure the DNS configuration on a computer running Windows XP quite easily by following these steps:

  1. Open Network Connections, right-click the active local area connection, and choose Properties.

  2. On the General tab of the Properties dialog box, select Internet Protocol (TCP/IP), and select Properties.

  3. In the Internet Protocol (TCP/IP) Properties dialog box, shown in Figure 8-14, select Obtain DNS Server Address Automatically, or select Use The Following DNS Server Addresses and type the IP address of the DNS server.

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    Figure 8-14: Set DNS properties.

  4. If you need to configure an alternate DNS server address and you have configured the computer to obtain its IP and DNS server addresses automatically, on the Alternate Configuration tab, click User Configured, and type a preferred and alternate DNS server address. Click OK when you are done. (The Alternate Configuration tab appears only if you have configured the computer to obtain its IP address and DNS server addresses automatically.)

  5. To configure advanced DNS settings, on the General tab, select Advanced.

  6. In the Advanced TCP/IP Settings dialog box, select the DNS tab.

  7. In the DNS Server Addresses, In Order Of Use list, note the configured DNS server addresses. Use Add, Edit, or Remove to make configuration changes to the DNS servers listed. Use the arrows to move a DNS server up or down the list. See Figure 8-15.

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    Figure 8-15: Configure advanced DNS settings.

  8. Click OK or Close to close the dialog boxes.

WINS

In addition to DNS, WINS is sometimes employed on a network. WINS servers resolve NetBIOS names to their associated IP addresses. NetBIOS names allow computers with older operating systems, such as Windows NT, Windows Me, and Windows 98, to participate in a network and to access resources. NetBIOS names are unique, and the name is generally a “friendly” name such as Server01 or Computer22.

Note

Not all networks use WINS servers. WINS integration is necessary only if the network includes computers running older operating systems.

If the network includes a WINS server, if you believe (because of results of ping, ipconfig /all, tracert, or other command-line tests) that an incorrect WINS configuration is preventing a user or users from resolving NetBIOS names to IP addresses, and if you have verified the IP address of the WINS server and that it is online, you should check the WINS settings on the local computer. You can view and reconfigure the WINS configuration on a computer running Windows XP quite easily by following these steps:

  1. Open Network Connections, right-click the active local area connection, and choose Properties.

  2. On the General tab of the Properties dialog box, select Internet Protocol (TCP/IP), and select Properties.

  3. In the Internet Protocol (TCP/IP) Properties dialog box, shown in Figure 8-14, click Advanced.

  4. In the Advanced TCP/IP Settings dialog box, select the WINS tab. Use Add, Edit, or Remove to make configuration changes to the WINS servers listed. Use the arrows to move a WINS server up or down the list. Leave the NetBIOS default settings, as shown in Figure 8-16. Click OK.

    click to expand
    Figure 8-16: Configure advanced WINS settings by using the Advanced TCP/IP Settings Properties dialog box.

  5. If you have configured the computer to obtain its IP address and DNS server address automatically and you need to configure an alternate WINS address, on the Alternate Configuration tab in the Internet Protocol (TCP/IP) Properties dialog box, click User Configured, and type a preferred and an alternate WINS server address. Click OK. Click Close.

    Exam Tip

    For the exam, make sure you understand how to enable automatic configuration of DNS servers and where you would go to specify particular DNS servers. Also make sure you know how to enable WINS.

LMHOSTS

An LMHOSTS file is a text file located on the local computer that maps NetBIOS names to their IP addresses for hosts that are not located on the local subnet. In Windows XP Professional, that file is located in the %Systemroot%\System32\Drivers\Etc folder.

LMHOSTS files can be manually updated and are useful in small networks where IP addresses change infrequently, or for networks with resources that have static IP addresses. When configuring WINS servers, make sure the Enable LMHOSTS Lookup check box is selected. LMHOSTS files serve as a backup for WINS servers.

HOSTS

HOSTS files are local text files that map host names and FQDNs to IP addresses. They are also located in the %Systemroot%\System32\Drivers\Etc folder. Figure 8-17 shows a sample HOSTS file.

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Figure 8-17: A HOSTS file maps host names and FQDNs to IP addresses.

Computers on the network are identified with their IP addresses. If a computer using a HOSTS file cannot connect to another using its host name, check this file for a bad entry.

Lesson Review

The following questions are intended to reinforce key information presented in this lesson. If you are unable to answer a question, review the lesson materials and try the question again. You can find answers to the questions in the “Questions and Answers” section at the end of this chapter.

  1. You are troubleshooting a connectivity problem on a small home office workgroup that includes four computers connected through an Ethernet hub. Each computer is connected directly to the Internet, and all computers should retrieve all TCP/IP addressing information automatically. One of the users complains that she can access other computers on the network but cannot access any websites. The other three computers are working just fine. You verify that the computer in question does not reach any websites when you type in the URL. However, you can get to websites when you type the actual IP address. You use the ipconfig /all command on each computer and determine that the computer that cannot access websites has different DNS servers listed than the other three computers. What is the likely problem?

  2. You ping the other computers by IP address. The user at Computer1 cannot access any workgroup resources but is able to access the shared printer connected directly to her computer; the other three computers can access all workgroup resources except for resources on Computer1, including the shared printer. What is most likely the problem?

    1. APIPA is in use.

    2. The network bridge is corrupt.

    3. The configured DNS server is not available.

    4. The Ethernet cable on Computer1 is disconnected from the NIC or the hub.

Lesson Summary

  • DNS and WINS are automatic name resolution services that resolve computer names to IP addresses. DNS is the native name resolution mechanism used on the Internet and on Windows Server 2003–based networks. WINS is used on networks that support previous operating systems.

  • HOSTS files are local text files that map host names and FQDNs to IP addresses. You can think of them as the manual equivalent of DNS.

  • LMHOSTS files are local text files that map NetBIOS names to their IP addresses. You can think of them as the manual equivalent of WINS.




McDst Self-Paced Training Kit (Exam 70-272(c) Supporting Users and Troubleshooting Desktop Applications on a[... ]ystem)
McDst Self-Paced Training Kit (Exam 70-272(c) Supporting Users and Troubleshooting Desktop Applications on a[... ]ystem)
ISBN: N/A
EAN: N/A
Year: 2006
Pages: 237

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