Configuring Central Automatic Configuration Servers


Automatic configuration and automatic proxy enable you to change user settings from a central location after you deploy Internet Explorer. This can be useful if you expect the needs of your users or your organization to change frequently.

On the Connections tab in the Internet Options dialog box, you can specify that Internet Explorer should check periodically for changes to the automatic configuration files, and then refresh user settings as needed.

You can also set these options before deployment by using the Internet Explorer Customization wizard. The following illustration shows the Automatic Configuration screen of the wizard, where you can set automatic detection, automatic proxy, and automatic configuration settings.


Information about setting up your servers for this feature is contained in this chapter. Information about setting options in the browser and in the Customization wizard are contained in Chapter 21 , "Using Automatic Configuration and Automatic Proxy. If you plan to use automatic configuration, you will need to configure servers on your intranet. To configure central management servers, you need to have the following:

  • Web-server software, such as Microsoft Internet Information Server (IIS)

  • Automatic configuration and automatic proxy files on the server at the URLs necessary for automatic browser configuration

The number of automatic browser configuration servers you require can vary according to the size and demands of your organization. If your organization is large, you might need to configure automatic browser configuration servers for each domain. For example, you could specify automatic browser configuration for user groups in domain 1 as follows:


You would install a Web server at http://domain1\_server and then copy the < usergroup.ins and < usergroup >.cab files and proxy1.pac to the server at http://domain1\_server/autoconfig. When users in domain 1 start Internet Explorer, it reads the appropriate automatic configuration files and the auto-proxy file residing at http://domain1\_server/autoconfig.

Note Whenever you update and post an Internet settings (.ins) file to a server, you should also copy any cabinet (.cab) files that have also changed.

Automatic Detection of Browser Settings (Corporate Administrators)

You can configure your network so that Internet Explorer is customized automatically the first time it is started. This can help reduce administrative overhead and potentially reduce help desk calls about browser settings.

Automatic detection of browser settings, which is based on Web Proxy AutoDiscovery (WPAD), is supported by both Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS). With the appropriate settings, DHCP servers that support the DHCPINFORM message and DNS servers can automatically detect and configure a browser's settings.

Automatic detection of settings builds on existing automatic configuration technologies, in which a browser can be configured from a central location with an IEAK profile or a JavaScript proxy configuration (.js, .jvs, or .pac) file.

With automatic detection, the browser can now be automatically configured when it is started, even if the browser was not first customized by the administrator. For example, if a user were to download a noncustomized browser from the Internet, instead of installing a customized version from the corporate servers, automatic detection can automatically configure and customize the user's browser.

To specify in the IEAK that you want to set up automatic detection of browser settings, select Automatically detect settings on the Automatic Configuration screen of the Internet Explorer Customization wizard.

Automatic Detection of Browser Settings for DHCP and DNS

A DHCP server enables the administrator to centrally specify global and subnet-specific TCP/IP parameters and to define parameters for clients by using reserved addresses. When a client computer moves between subnets, it is automatically reconfigured for TCP/IP when the computer is started.

DNS is a set of protocols and services on a TCP/IP network that allow users to search for other computers by using hierarchical user-friendly names, often known as "hosts," instead of numeric IP addresses.

Using DHCP with automatic detection works best for local area network-based (LAN-based) clients, while DNS enables computers with both LAN-based and dial-up connections to detect their settings. Although DNS can handle network and dial-up connections, DHCP provides for faster access to LAN users and allows greater flexibility in specifying configuration files.

To enable automatic detection of browser settings, you need to configure specific settings on DNS servers, DHCP servers, or both.

Enabling Automatic Detection of Browser Settings on DHCP

To set up automatic detection of browser settings on a DHCP server, you need to create a new option type with a code number of 252. Your DHCP server must support the DHCPINFORM message.

Note Depending on your type of DHCP server, the option names may vary slightly.

Cc939850.prcarrow(en-us,TechNet.10).gifTo add a new DHCP option type

  1. On the DHCP Options menu, click Defaults .

  2. In the Option Class list, click the class for which you want to add a new option type, and then click New .

  3. In the Name box, type a new option name.

  4. In the Data Type list, click the String data type.
    For the default value of the string, type the URL that points to your configuration file. This file can be a .pac, .jvs, .js, or .ins configuration file.
    Examples: http://marketing/config.ins http://\#\#\#.\#.\#\#\#.\#/acc

  5. In the Identifier box, type the code number 252 to associate with this option type.

  6. In the Comment box, type a description.

Enabling Automatic Detection on DNS

To enable automatic detection of browser settings on DNS, you need to configure either the host record or CNAME "alias" record in the DNS database file.

Host Record

A host record is used to statically associate host (computer) names to IP addresses within a zone. A host record contains entries for all hosts that require static mappings, such as work stations, name servers, and mail servers.

The syntax for a host record has this form:

<host name> IN A <ip address of host>

The following list shows some examples.

Host name



Host IP address










CNAME Record

These records are sometimes called "aliases" but are technically referred to as "canonical name" (CNAME) entries. These records allow you to use more than one name to point to a single host. Using canonical names makes it easy to do such things as host both an FTP server and a Web server on the same computer.

Cc939850.prcarrow(en-us,TechNet.10).gifTo configure a DNS database file for automatic detection of browser settings

  • In the DNS database file, enter a host record named wpad that points to the IP address of the Web server that contains the .pac, .jvs, .js, or .ins automatic configuration file.
    Enter a CNAME alias named wpad that points to the name (the resolved name, not the IP address) of the server that contains the .pac, .jvs, .js, or .ins automatic configuration file.

    Note After the record is added and the database file is propagated to the server, the DNS name wpad. domain .com should resolve to the same computer name as the server that contains the automatic configuration file.

When using DNS, Internet Explorer constructs a default URL template based on the host name wpad - for example:

Therefore, on the Web server wpad , you must set up a file or redirection point named wpad.dat, which delivers the contents of your automatic configuration file.