To create an optionĀ 252 entry in DHCP

  1. Click Start, point to All Programs, point to Administrative Tools, and then click DHCP.

  2. In the console tree, right-click the applicable DHCP server, click Set Predefined Options, and then click Add.

  3. In Name, type WPAD.

  4. In Code, type 252.

  5. In Data type, select String, and then click OK.

  6. In String, type https://Computer_Name:Port/wpad.dat where:

    • Computer_Name is the fully qualified domain name of the ISA Server computer.
    • Port is the port number on which automatic discovery information is published. You can specify any port number. By default, ISA Server publishes automatic discovery information on port 8080.
  7. Right-click Server options, and then click Configure options.

  8. Confirm that Option 252 is selected.


Perform this task on the relevant DHCP server.
When you specify the OptionĀ 252 string, be sure to use lowercase letters when typing wpad.dat. For example, if you type https://isaserver:8080/Wpad.dat, the request will fail. ISA Server uses wpad.dat and is case-sensitive.
You do not need to create anything specifically for Wspad.dat. Wspad.dat uses the same 252 option as wpad.dat, and modifies the wpad.dat name to Wspad.dat as required.