Automatically detect proxy server / automatically detect settings

[member 141630]

Hi,
By what mechanism does Explorer use, to automatically detect a Microsoft Proxy server (either ISA or Proxy)?

I know this automatic feature works well, but how does it work? I accept its a broadcast of some kind, but some technical info would be useful as I have a network which is routed into 3 subnets (via cisco gear) and wish for the automatic detection to work over a routed network - The Cisco side is OK as I already have DHCP broadcasts routed fine, but cant get the automatic detection part sorted out.

This feature doesnt seem to be documented anywhere....

Kindest Regards and thanks in advance

PhilB

 

[EvilKlown]

1st Make sure that FIrewall Client option is "Enabled", this will use a query to DNS to find the ISA server.
2nd Firewall client needs to be DHCP to use this method
3rd right-click DHCP server's name, then click "Set Predfined Options" command, click "add"
Next, in the "Option Type box type
NAME: WPAD
DATA TYPE: STRING
CODE: 252
DESCRIPTION: Wpad Entry (or whatever you want)
now click "OK"
4th In the "Predefined Options and Values" box type in the string value

http://ISA_Server_Name:Autodiscovery_Port_Number/Wpad.dat

click "OK"

5th In the left pane of the DHCP console, right-click "Scope Options" node under scope of interest, then click the "Configure Options" command. You will now see a box "Predefined Options and Values" box.
Now, under the "General" or "Option Name" tab scroll down to "252 WPAD" and place a checkmark on it, now click "OK"

This will only work if your Scope is configured properly for your client you want accessing the firewall.


Now, you can try DNS also:

Open DNS
GOTO "Forward Lookup Zones"
Click "New Alias"
In "New Resourcer Record" type "wpad" in the "Allias Name" text box and type in the FQDN for the ISA server in the "Fully Qualified Name For Target Host" text box., then click okay and be sure to include the trailing periods!

Lastly test it. from the command prompt at DNS server type NSLOOKUP WPAD.<YOURDOMAINNAMEHERE> and press &quot;Enter&quot; Teh &quot;wpad&quot; CNAME entry should resolve to your ISA server.

Good luck!

Evil Klown



You have to configure DNS

 

[member 141630]

Hi,
Thanks - this is very useful information, but consider the following set up..


A Microsoft NT4 box running IIS/Proxy2.
A Client running Windows 98
NO proxy client installed on server or workstation
Client is running IE5 and in the Connection Options, Lan Settings it is configured to 'automatically detect settings'. With this option checked, Internet Explorer automatically finds the proxy server.... obviously by using a broadcast, but what sort of broadcast is used?

 

[fluid11]

I don't know what happens when their is no client software installed, but if your running the Firewall Client on a workstation, autodiscovery is done by either querying either a DHCP server via a DHCPINFORM message or directly querying a DNS server via a DNS query for the name wpad.&quot;domain_name&quot;.


ChrisP