Lmhosts File

The Lmhosts file resolves IP addresses with domain names. When setting up for RAS connectivity, you need to add the IP address and domain of each Microsoft Exchange Server computer to the Lmhosts file on the RAS server.

If the Lmhosts file already exists, it will be located in the Winnt40\System32\Drivers\Etc directory. If this file does not exist, you need to create it. If you are not familiar with Lmhosts files, you should review the Lmhosts.sam file provided with Windows NT. This sample file is also located in the Winnt40\System32\Drivers\Etc directory.

Enabling Lmhosts Lookup Functionality

To work with the Lmhosts file, you must first enable Lmhosts lookup functionality.

1. In Control Panel, double-click Network.
2. Select the Protocols tab.
3. Select TCP/IP Protocol, and then choose Properties.
4. Select the WINS Address tab, and then select the Enable LMHOSTS Lookup check box.

Modifying Lmhosts Files

You must edit the Lmhosts file to include the server names and IP addresses for each Microsoft Exchange Server computer that you plan to connect using the Dynamic RAS Connector.

The file should include the server name and the IP address of the NIC from the opposing Microsoft Exchange Server computers. The LMHOSTS entry should be followed by a #PRE entry, and a #DOM:<domain name> entry if the server specified is a primary domain controller (PDC) or a backup domain controller (BDC) responsible for validating logons. For example, the Lmhosts file for each of three Microsoft Exchange Server computers connected through a Dynamic RAS Connector would contain the following lines:

Guidelines for Working with Lmhosts Files

When working with Lmhosts files, you should do the following:

• When you reach the bottom of the file, press ENTER several times to create blank lines before saving the file.
• Use only uppercase characters.
• Save the file without an extension (such as the default .txt extension that is automatically appended by Notepad).
• Save the Lmhosts file as a text file (but if Notepad is used to save the file, make sure that Unicode is not selected as the file type in the Save file dialog box).
• Verify that the name of the Lmhosts file is spelled correctly.

Verifying the Lmhosts File

You can verify that the contents of the Lmhosts file can be interpreted by Windows NT using the Nbtstat command.

Complete the following steps to verify the Lmhosts file.

1. At the command prompt, type Nbtstat -R. (Note that the R must be uppercase).
This will purge the existing cache and load any entries in the Lmhosts file.
2. Type Nbtstat -c to view the contents of the cache.

The Microsoft Exchange Server computer names entered when generating the Lmhosts file should be displayed in the cache. If not, the Lmhosts file or Windows NT is not correctly configured.