How does one take advantage of that "Automatically Determine Proxy Settings" option?

[yukichigai]

In my further quest to make the company network secure and free of porn virii of doom, I have set up HTTP blocking on all default assigned DHCP IP leases, with a proxy that requires a login for users that actually need HTTP access. A few computers have static IPs that fall out of the HTTP block range by design, since their use would likely cripple the proxy system. (and because I trust them not to act like re-res online)

The difficulty I'm having is thus: IE has an option called "automatically determine proxy settings" or something like that, which I'd very much like to take advantage of. Setting all the blocked systems to use the proxy manually is a pain in the tookus. The problem is that I have no idea how IE determines the settings automatically. I'm hoping it's something I can set on the DHCP server, or the main DNS server, or something like that. Does anybody know how I can do this, without forcing the exempt systems to use the proxy as well?

 

[EatSpam]

Google "transparent proxy"

 

[yukichigai]

I should have mentioned that I'm pretty much restricted to using Microsoft-based products. All the "transparent proxy" results I got were for Linux programs. Really good Linux programs, but Linux all the same.

 

[Wizkid]

Maybe you can do something with an autoproxy.pac file?

 

[Wizkid]

http://www.grok.co.uk/forum/viewtopic.p...2&sid=2aa9d18d8f9845df34a407f680b84d1a

 

[Garion]

What you're looking to configure is WPAD - Web Proxy Automatic Detection. It's really just a different way to serve a proxy PAC file to an IE browser.

I could give you a long-winded explanation, but a few links would probably be better.

How to configure browsers for WPAD

WPAD at Microsoft technet

We use this as a fallback for foreign browsers that come in and don't have our standard proxy settings. Works like a champ!

If you need help writing a PAC file, let me know and I'll get you an example.

- G

 

[spidey07]

I thought you just set it as an option in DHCP??? Dhcp tells the machine the proxy settings.

could be off, never used it.

 

[yukichigai]

Yeah, I'm not quite sure how to write a PAC file. I know you can use JavaScript, but I don't know if it requires some special encoding or just requires you to rename the extension to .pac. I've got no problems with JavaScript itself -- I'm a CS major, so I had to learn it eventually -- just the requirements of a PAC file.

 

[ktwebb]

Running a windows 2000 or 2003 domain? GPO. Script the proxy settings and remove their access to change them.

 

[yukichigai]

Okay, I may need some help with the PAC file. More accurately, one particular section of it.

I need to specify in the file that a range of IP addresses be prompted to use the proxy. (192.168.0.50 - 192.168.0.100) I'm not quite sure how to do this, since I don't know what functions are available to me. My best guess is something along these lines:

if(atoi(substring(myIpAddress(),10,3))) > 100) return "DIRECT";
etc....

Of course I don't know if atoi is available for a proxy script. Anybody have a clue?

EDITx2: Went back, reread one of the links Garion gave me, got the script accessable.

EDIT: Win2k domain. We'll be switching to a 2k3 domain in November.

EDITx3: Nevermind, figured it out. Wound up using regular expressions. For anybody who cares, the solution was thus:

var regexp = /192\.168\.0\.[5-9][0-9]/;
if(regexp.test(myIpAddress())) return "PROXY <etc>";

Along with a manual entry for 192.168.0.100. So... yeah, go me.