Customizing Web Proxy Auto-Discovery

When WPAD is enabled in Cache > Client Accelerator, the appliance activates WPAD listening on all IP addresses configured for client acceleration.

The appliance answers WPAD requests from browsers by returning a .DAT file that contains standard WPAD JavaScript* configuration instructions for the browser.

Procedures for configuring browsers to request and use WPAD information vary. Internet Explorer supports both automatic detection of WPAD settings and automatic configuration files retrieved from known URLs. Netscape* supports only the latter WPAD configuration method.

Internet Explorer's automatic detection feature requires that the DNS server databases which the workstations use contain wpad.domain.com entries that resolve to the appropriate appliance forward proxy address. See How the Appliance Handles WPAD Requests.

If your proxy services require additional browser configuration, you can create a default configuration file for all WPAD requests, or you can customize any or all of the system-created .DAT files. See Creating a Default WPAD.DAT Configuration File and Customizing System-Created WPAD DAT Files for details.


How the Appliance Handles WPAD Requests

When the appliance receives a WPAD request, it looks in \ETC\PROXY\DATA for a WPAD.DAT file. This file exists only if an appliance administrator has created it.

If the file is found, the appliance returns it to the requesting browser regardless of which client acceleration IP address the request was received on. Thus, the same WPAD configuration is used for all requesting browsers.

If the file is not found, the appliance returns a .DAT file created by the caching system for the specific IP address through which the request was received.

The appliance automatically creates and stores a WPADxx.DAT file in \ETC\PROXY\DATA for each IP address configured for client acceleration. Files are automatically named with successive numbers, as shown in the following table.

Order in Which IP Address Are Enabled for Client Acceleration WPAD Configuration Filename

First IP address enabled

WPADX1.DAT

Second IP address enabled

WPADX2.DAT

Third IP address enabled

WPADX3.DAT

Creating a Default WPAD.DAT Configuration File

You can create a default configuration file that will be sent in response to all WPAD requests.

This file might provide backup proxy references by containing a list of all appliance addresses configured for client acceleration. Alternatively, it might redirect all WPAD clients to use only a specific IP address for proxy services. Or it might contain additional configuration instructions to browsers using WPAD.

To create a WPAD.DAT file, complete the following steps:

  1. If you have not already done so, enable at least one appliance IP address for client acceleration in Cache > Client Accelerator and apply the settings.

  2. Start an FTP client on a workstation that has access to the appliance.

    For help, see Starting an FTP Session with the Appliance.

  3. Point the FTP client to one of the appliance's IP addresses.

  4. Enter the following command:

    get /etc/proxy/data/wpadx1.dat

    The .DAT file for the first client accelerator is transferred to the FTP client's default directory.

  5. Modify the file using an ASCII editor. Be sure to conform to JavaScript programming conventions.

    Information about WPAD configuration file content and functionality is available in various locations on the Web. Be aware that some conventions are browser-specific.

  6. Use the PUT command to rename the modified file and place it back on the appliance by entering the following command:

    put wpadx1.dat /etc/proxy/data/wpad.dat

    The appliance now answers all WPAD requests by returning the WPAD.DAT file you created.


Customizing System-Created WPAD DAT Files

You can customize the system-created, IP address-specific .DAT files so that browsers are configured differently depending on the IP address through which the WPAD request originates.

To customize any of the system-created .DAT files on your appliance, complete the following steps:

  1. If you have not already done so, enable at least one appliance IP address for client acceleration in Cache > Client Accelerator and apply the settings.

  2. Start an FTP client on a workstation that has access to the appliance.

    For help, see Starting an FTP Session with the Appliance.

  3. Point the FTP client to one of the appliance's IP addresses.

  4. Enter the following command, where xx represents the system-assigned ID number of the file starting with x1:

    get /etc/proxy/data/wpadxx.dat

    The .DAT file for the first client accelerator is transferred to the FTP client's default directory.

  5. Modify the file using an ASCII editor. Be sure to conform to JavaScript programming conventions.

    Information about WPAD configuration file content and functionality is available in various locations on the Web. Be aware that some conventions are browser-specific.

  6. Use the PUT command to copy the file back to the appliance by entering the following command, where xx represents the system-assigned ID number of the file starting with x1:

    put wpadxx.dat /etc/proxy/data/wpadxx.dat

  7. Repeat this procedure for each .DAT file you need to customize.

The appliance now answers WPAD requests according to the customizations you have made.