Firewall Clients

A Firewall client is a computer with Firewall Client software installed and enabled. The Firewall client runs Winsock applications that use the Microsoft Firewall service of ISA Server 2004. Whenever a Winsock application running on a Firewall client attempts to send a request to a computer, the client checks its local address table (LAT) to see if the specified computer is included in an IP address range in the LAT and can be recognized as a local destination. Addresses specified in the local routing table on the Firewall client are also considered local. If the destination is local, the Firewall client sends the request directly to the computer. If the destination is not local, the request is sent to the Firewall service on an ISA Server computer. The Firewall service handles the request, forwarding it to the appropriate destination, as permitted. The Firewall Client software can send Windows user information, which is required for authentication purposes, to the ISA Server.

Setting up a Firewall client does not configure individual Winsock applications. Instead, it uses the same Winsock dynamic link library (DLL) that the other applications use. The Firewall client then intercepts the application calls and decides whether to route the request to the ISA Server computer.

You can install Firewall Client software on client computers that runWindows 95, Windows 98, Windows Millennium Edition (Me), Windows NT 4.0, Windows 2000, Windows XP, or Windows Server 2003. 16-bit Winsock applications are supported, but only on Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003.

Firewall clients are supported only if the Firewall service is running.