How to Maintain Additional LAT Entries for an ISA Firewall Client (268326)

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The firewall client setup program installs a file named Msplat.txt into the Program Files\Microsoft Firewall Client folder or the default folder specified during setup, or in a location based on the previous install location of the client software on the client computer.

The Msplat.txt file contains the LAT, which defines the IP addresses that are located on the internal network. In some situations, the LAT that the server downloads may not completely define some addresses that a particular client needs to gain access to the internal network. This file is regularly updated by the ISA Server computer, so any changes made manually at the client are overwritten at the next update.

This article describes how to create a file named Locallat.txt and add local addresses to the file. By doing this, you maintain a separate list of IP addresses that the client considers internal.

You can use a text editor to create a custom client LAT file named LocalLAT.txt and place it in the same folder in which the client software is installed (Program Files\Microsoft Firewall Client). This file can contain any additional network ranges needed for this client and should be in the same format as the MSPlat.txt file. The client uses both the Msplat.txt and Locallat.txt files to determine which IP addresses are part of the internal network and which are on the Internet.

The Locallat.txt file should contain IP addresses in pairs. Each address pair defines either a range of IP addresses or a single IP address.

Example:

The first entry is an IP address range and the second entry is a single IP address. Note that in the second entry, the second part of the pair is an IP address and not a subnet mask.

   10.51.0.0          10.51.255.255

   10.52.144.103      10.52.144.103