DHCP not providing option 252 since upgrade to 2008 R2

Question

We have been using DHCP option 252 to provide details of the WPAD.DAT file for proxy auto config for the past 4 years and it has been working well. We recently upgraded (replaced)
out DC from an old W2k3 server to a 2008 R2 server. 
The DHCP options were identical as we exported them from the one server and imported them to the new server, but since the change over we have not been able to go proxy auto config to work. 
The clients (combination of XP and Win7) don’t even seem to be trying to access the file. 
It appears that the DC is not providing the details to the clients.
Has anyone got proxy auto config working with a 2008 R2 DHCP server? 
I have been working on this for a couple of weeks and we know the web server side is working fine. 
I have tried removing option 252 and recreating it, but that does not help.
Any ideas?
Steve

Answer 1

Hi Steve J B  ,
Thanks for posting here
Please check if this issue could be resolve on XP client with the article below:
953761  Some DHCP Options are not recognized on a Windows XP SP3-based client computer when the DHCP server offer includes option 43
http://support.microsoft.com/default.aspx?scid=kb;EN-US;953761
If this problem continues , then please capture packet while the client requests an IP address from the DHCP server by Wireshark and filter the result with filter
string “ bootp.options.type == 252  ”
Meanwhile, please following workaround to configure DNS to set the Proxy Autodiscovery information.
To implement web proxy auto-discovery in your environment, refer to the following steps:
1.      
Enable "Automatically detect settings" in IE.
a)     
In IE window, click "Tool"-->"Internet Options".
b)     
On "Connections" tab, click "LAN settings".
c)      
In "Local Area Network (LAN) Settings" window, ensure "Automatically detect settings" is checked.
2.      
Add "WPAD" record in DNS server:
a)     
Start the DNS snap-in.
b)     
In the console tree, click your server name, and then click Forward Lookup Zones.
c)      
Right-click the forward lookup zone that you want to support Web Proxy client Autoconfiguration, and then click New Alias.
d)     
Type wpad in the Alias name box.
e)     
Type in the Fully Qualified Domain Name(FQDN) of the proxy server computer's internal interface. Use the Browse button to minimize the chance of making an error.
NOTE : The proxy Server computer must already have a Host (A) address record before you create an Alias (CNAME) record.
f)      
Click OK.
And please post the result after following above settings.
The following are the details of how the Web Proxy Auto-Discovery (WPAD) works with DNS server for you reference:
1.      
With the auto detect setting enabled, when IE starts and tries to access a website, it will try to detect the proxy server.
2.      
The computer will send DNS name query for the name "WPAD". If a record called "wpad" is added to the DNS server, DNS server will respond with the IP address of that name and then client
will try to access http://wpad/wpad.dat. If client locates the server through
DNS, only the default port 80 will be used and we cannot specify any other ports.
3.      
Client will find the proxy server from the wpad.dat file after getting the file by accessing the URL:
http://wpad/wpad.dat. At last, the client will send the request to the proxy server
to access the website.
Thanks.
Tiger Li
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