A+ Certification / Beginners

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The LMHOSTS file

If you don't have a WINS server, and an application you are running requires the use of a NetBIOS name (computer name), then you need to use what is known as the LMHOSTS file. The LMHOSTS file resides on each computer and is used to resolve, or convert, computer names to IP addresses. This file exists on each system on the network - you simply need to add an entry for the computer name and the corresponding IP address for each system you want the file to resolve.

Windows 2000/XP/2003 stores the file in %systemroot%\system32\drivers\ etc. In Windows 2000/XP/2003, the folder has an existing LMHOSTS file that you can use as a sample, but it has a .SAM extension that needs to be removed because the true LMHOSTS file has no extension.

Fully qualified domain names (FQDN)

The other type of name that can be assigned to the computer when you are running a TCP/IP network is a host name, or a Fully Qualified Domain Name (FQDN). FQDNs are used when you run a TCP/IP- or Internet-based application like FTP, e-mail, or Web browser applications. For example, to navigate to my Web site via your favorite Web browser, you would type www.gleneclarke.com - this is an example of an FQDN. An FQDN is an Internet-style name that needs to be converted to an IP address in order for communication to occur.

The point is that when you use a computer name or an FQDN on a TCP/IPbased network, the names always need to be converted to the actual IP addresses. Again, the converting of names (either computer names or FQDNs) to IP addresses is the process referred to as name resolution. There are a few techniques for FQDN resolution, and some are more popular than others. The following sections describe the name resolution techniques and their purposes.

DNS

DNS stands for Domain Name System and is the desired name resolution technique for resolving (converting) fully qualified domain names to IP addresses. Remember that FQDNs are the names that are used with Internetbased applications, such as e-mail and Web browsers. DNS is like a big database of FQDNs and their matching IP addresses. Think of this database as having two columns - one for the FQDN and the other for the IP address.

When you are running Internet or TCP/IP applications and you type in a fully qualified domain name, your computer sends a query, which is just a question, to the DNS database asking something like this: "I am trying to connect to www.gleneclarke.com. Do you have the IP address that matches this FQDN?" The database looks up the FQDN and returns the IP address to your computer, and your computer then connects to that IP address.

The big question is where is the database stored? The database is stored on what are called DNS servers. These servers are where the actual records are located and also where each client computer on your network sends its name queries.

To configure a Windows XP client to use a DNS server, you will add the IP address of the DNS server while configuring TCP/IP (refer to the section "Configuring TCP/IP in Windows 2000/XP/2003," earlier in this tutorial). Notice also that in the newer versions of Windows, the DNS server option is on the same screen as where you assign the IP address for a computer - it shows how critical DNS is to today's computing! To configure a Windows client to use DNS, follow these steps:

1. In Windows 2000, choose Start → Settings → Control Panel → Network and Dial Up Connections. In Windows XP/2003, choose Start → Control Panel → Network and Internet Connections → Network Connections.
2. Right-click your Local Area Connection and choose Properties.
   The local area connection Properties dialog box appears.
3. In the item list, select TCP/IP and click Properties.
4. In the TCP/IP Properties dialog box, select the Use the Following DNS Server Addresses option and type the IP address of your DNS server.
5. Click OK twice to close the dialog boxes.