Configuring WPAD (option 252)

The Web Proxy Auto-Discovery (WPAD) protocol is used by web browsers to locate a Proxy Auto-Config (PAC) file automatically.
The WPAD protocol can use a DNS or DHCP server to locate a PAC file. DHCP detection involves the URL being pushed to the user in the DHCP assignment, while DNS detection is based on an informed guess, using known information about the DNS. A web browser that supports both methods checks the DHCP assignment first, and then attempts the DNS method. If the browser is unable to load a PAC file through the DHCP or DNS methods, it will allow direct Internet access.
Note: The PAC file must have the file name wpad.dat for the DNS method to function.
  1. Enter global configuration mode. 
    device# configure terminal
  2. Configure an address pool in the DHCP server and enter DHCP server pool configuration mode. 
    device(config)# ip dhcp-server pool cabo
  3. Enter the option command followed by the full network location of the PAC file. 
    device(config-dhcp-cabo)# option 252 ascii http://172.26.67.243:8080/wpad.dat
  4. Enter the show ip dhcp-server address-pools command to view the configured network location of the PAC file. 
    device(config)# show ip dhcp-server address-pools 

  Showing all address pool(s):
                    Pool Name:  test
 Time elapsed since last save:  00d:00h:01m:21s
Total number of active leases:  1
           Address Pool State:  active
      Pool Configured Options:
                        lease:  1 0 0
                      network:  50.50.50.0 255.255.255.0
        option 252 (WPAD    ):  http://172.26.67.243:8080/wpad.dat
Parent topic: DHCP Servers