IE "Automatically detect settings"

Peter Ortner port at iname.com
Mon Jan 6 06:57:04 EST 2003


This functionality is documented in the IEAK, IIRC.

When "Automatically detect settings" is ticked in IE, it tries the
following:

* If the PC is configured to do DHCP, then it will query the server. If
the response includes a string with id 252, then it uses this to
retrieve a configuration file.

* If this fails, then the PC will attempt to resolve the name wpad. It
will start in its current domain, and work back through. Eg, if the PC
is called bob.cs.anu.edu.au, it will attempt to resolve
wpad.cs.anu.edu.au, followed by wpad.anu.edu.au, etc. If this resolves
the name wpad, then IE will attempt to retrieve wpad.dat via http from
the root of the server. You should probably redirect this to the
configuration file.

* If this yields no success, then IE goes direct.

The configuration file can be either a .ins file, or a .pac file. Simon
Haddon has already commented on .pac files, in another e-mail. .ins
files are IE configuration files, which can specify all sorts of
settings, such as Outbreak Express mail servers, title bar and icons for
IE, dial-up settings, etc. Check the IEAK for more details.

You can do some pretty cool things with .pac files, and here is an
example: http://www.schooner.com/~loverso/no-ads/

So, yes, you can emulate this functionality using a real Internet
operating system. I found that the DNS method was the most reliable. As
for other ISA functionality, there are various extensions/hacks for
squid, etc, which can do accounting and access control.

So yes, there is a better way. :-)

Michael James wrote:

> When a default Windows install uses  "Automatically detect settings"
>  it relies on DHCP to provide the address of an "ISA"
>  (Internet Security and Acceleration) server.
> The ISA server gives it a config file for IE with the proxy setting.
>
> Has this been unpicked by the open source community?
> Is the ISA functionality available from a Linux server?
>
> Or is there simply a better way?
>




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