Summary #

The preferred method of setting up Proxy Auto Detect is with DNS as seen in this article – Proxy Auto Detect (WPAD) – but there are still some situations where the DHCP method can be useful.  The DNS method of Proxy Auto Detect uses the same proxy config for all computers on the network. The DHCP method can give different proxy settings to different DHCP Scopes. The limitation of the DHCP method is that it only works for IE and there are issues with Apple OSX clients. If you do setup the DHCP you should also setup Proxy Auto Detect with DNS.

More Information #

Users with Apple OSX & Windows DHCP Server: There is an incompatibility problem if you are using a Windows DHCP server and Mac OSX clients.  The Windows DHCP server uses null-termination for its’ DHCP strings.  According to the DHCP specification, this is allowed but not recommended.  Max OSX’s DHCP client does not know how to handle anull-terminated string properly.  The work around for this issue is tonot setup the DHCP option (indicated below) and only setup the DNS names.

First, you need to configure your DHCP server to hand out “option 252” when it’s asked for it: (These instructions are for Windows servers, but other platforms are very similar).

1. On your DHCP server, start the DHCP snap-in (Start -> Programs -> Administrative Tools -> DHCP)
2. Right-click the DHCP name, and then click Set Predefined Options
3. Click Add
4. Type wpad in the Name box
5. Select “String” in the Data Type box
6. Type “252” in the Code box
7. Click OK
8. Type “http://[IP Of SecureSchool]/wpad.dat” in the String box in the Predefined Option and Values dialog box, putting in the IP address of your SecureSchool appliance
9. Click OK