If anyone is using the Automatic Discovery for Web Proxy Clients, then you will know that you can deploy these settings either via DNS and or DHCP. For those who haven’t used this then here is a bit of an insight into how it works.

ISA 2004 and 2006 provides the ability for Web Proxy Clients to automatically locate the ISA Server to use for it’s clients requests. ISA Server uses the WPAD Protocol so that clients can locate the server that is hosting the Wpad.dat and Wspad.dat files. The Wpad.dat file is used by Web Proxy clients for automatic discovery information.

To make your proxy clients aware of it’s existance you can either use a DNS Ailias Entry or you can push the settings out via DHCP. First things first you need to configure Internet Explorer to use Automaic Discovery. Go to Tools > Internet Options > Connections > LAN Settings and tick Automatically Detect Settings.

On the ISA Server, I’m using ISA 2006, you need to goto Configuration > Networks > Network Tab. Right Click your “Internal Network” and then go to the Auto Discovery Tab. Place a tick in the Publish automatic discovery information for this network. You can test to see if you can get to the wpad.dat file by typing this URL into IE – http://servername:portnumber/wpad.dat and you should get the file.

Next you can either Configure a DNS Alias called WPAD and point that to the ISA box or you can configure the options on your DHCP Server. Now in my environment for some reason, which I am yet to work out, the DNS option seems to be a bit dodgy. So today I though I would configure the DHCP options, keeping in mind that remote access client will not be able to access the DHCP Server so this will not work for them, but for a Local Lan this will be fine, and an upside is that is provides faster access.

On your DHCP Server you need to Right Click the Server in the DHCP Manager Snap In and select Set Pre Defined Options, then click the Add Button. Name the Entry WPAD, Select String as the Data Type, and the code needs to be 252. The String Value needs to be this:

http://Computer_Name:Port/wpad.dat

Obviously substituting the computer name and port number to the ones relevant to your environment. Next you need to Right Click Server Options > Configure Options and then scroll right down to the bottom of the list until you find the 252 – WPAD Entry and place a tick in the box.

To make this work for my clients that already had DHCP Leases what I did was to go to the Address Leases and manually delete the current Leases and for the clients to options a new Lease and therefore the new Server Options. So far so good and it is all working extremely well.