Automatic discovery overview

Microsoft Internet Security and Acceleration (ISA) Server 2006 supports automatic discovery to allow Firewall clients and Web Proxy clients to automatically locate an ISA Server computer to use for client requests.

ISA Server uses the Web Proxy Automatic Discovery (WPAD) protocol, which allows automatic discovery of Web proxy servers. ISA Server uses WPAD to provide a mechanism for clients to locate a WPAD entry containing a URL that points to a server on which the Wpad.dat and Wspad.dat files are generated. The Wpad.dat file is a Java script file containing a default URL template, constructed by Internet Explorer. The Wpad.dat file is used by Web Proxy clients for automatic discovery information. The ISA Server WinSock Proxy Autodetect (WSPAD) implementation uses the Wpad.dat file, and creates a Wspad.dat file to provide automatic discovery information to Firewall clients. For more information about the WPAD protocol, see Web Proxy Auto-Discovery Protocol(http://www.microsoft.com/).

Configuring automatic discovery

There are several configuration steps involved in setting up automatic discovery support for clients:

1. Configure Web Proxy clients and Firewall clients for automatic discovery. For instructions, see Enable automatic discovery for Firewall clients and Enable automatic discovery for Web Proxy clients.
2. Create WPAD entries containing a URL that points to a WPAD server on which the Wpad.dat and Wspad.dat files are located. You can create a WPAD entry in Domain Name System (DNS), in Dynamic Host Configuration Protocol (DHCP), or in both. For instructions, see Create a WPAD entry in DNS.
3. Configure a WPAD server. The URL specified in the WPAD entry points to the WPAD server, which is the computer on which the WPAD and WSPAD files can be located. The following are possible configurations for the WPAD server:
4. • In the simplest configuration, the WPAD server is located on the ISA Server computer that will service client requests.
   • Alternatively, the WPAD server might be located on a computer separate from the ISA Server computer.
5. If the ISA Server computer will act as the WPAD server, configure ISA Server to listen for automatic discovery requests, by publishing automatic discovery information on a specified port.

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