IE "Auto Detect Settings" lagging initial internet connection, why?

Currently for all users within my organization when the "Auto Detect Settings" check box is selected under LAN Settings in IE Options the intial loading of a new page is extremely slow.

If Auto Detect Settings is turned on when a new browser window is opened or a new tab it takes about 30 seconds before the users browser connects to their home page or any webpage. Once the home page is loaded up the internet is very fast though. Its like it is trying to auto detect a proxy and timing out before it finds one then defaulting to the DNS or something.

This is occuring on all PC's running Windows XP IE 7 or IE 8 and Windows 7 PC's running IE 8.

Our PC's are on the 10.30.1.xxx subnet and have this problem. Our servers running on the 10.10.1.xxx and 10.20.1.xxx subets have the same Auto Detect Setting enabled in IE but do not experience this lag when initially loading a website.

Can anyone explain what the Auto Detect Settings function does or why it may be lagging the initial internet connection on our 10.30.1.xxx subnet? I am just looking for clues at this point since I dont even know where to begin. Should I look at Wireshark packet captures to look for a certain communication that may be timing out?

Thanks in advance
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AIC-AdminAsked:
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AIC-AdminConnect With a Mentor Author Commented:
Okay I think I found my own solution but it will be a few days before I can test.
Within my DNS server in my forward lookup zone there is a record for WPAD which has the setting "Full qualified domain name [FQDN] for target host: isa.ahc.net".
As well within our DHCP configurationunder Predefined Options we have an Option 252 WPAD created that points to String: http://ISA.ahc.net:80/wpad.dat.
I believe removing these two entries will correct my IE lag problems when establishing a new connection. Thanks to jtokarchuk for his assistance.
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jtokarchukCommented:
You are exactly rioght. When auto detect settings are on, every time you open a new connection (tab, browser, etc) your machine will actively search for a proxy server.

Resolution: uncheck everything in the LAN settings box. Even uncheck auto detect settings. You will notice that lag dissapear.
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jtokarchukCommented:
As far as to why on one subnet and not the other, not too sure. That's an odd one. Are you NAT ing over multiple subnets? Or are they comlpetely segregated?

Perhaps the DNS is not as snappy on the one subnet.
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AIC-AdminAuthor Commented:
Yes we do use NAT since we have multiple VLANS in place. We are using Juniper firewalls and Procurve switches. Whats ever more odd is that we have a Cymphonix Proxy device that we using but it does not sit in line between our user network switch and the firewall. I didnt mention that in the initial problem because with or without pushing traffic through our Cymphonix proxy we have this lag IF auto detect settings are turned on. So even when we specify a proxy with Auto Detect turned on the browser still sits and wait to auto detect a proxy before going through the designated Cymphnix proxy.
We used to have an ISA server that we have gotten rid of. I wonder if somewhere there is a residual configuration where the desktops are trying to locate our ISA server that no longer exists.  Any idea how I could tell if that is occuring?
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jtokarchukCommented:
ruin - cmd - proxycfg.exe -- does this show anything?

If not, try a netsh winsock reset, perhaps that will flush out any residual crap laying around.

Does a manual entry of proxy server with automatic discovery turned off work?
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AIC-AdminAuthor Commented:
when I run the proxycfg.exe command it just brings up Internet Options to the connections tab (which I have my Cymphonix proxy turned off right now).
I ran the netsh winsock reset command and rebooted my PC but that didnt help
If Automatically Detect Settings is turned off my internet runs fine whether I go through our Cymphonix proxy or not. If I am going through my Cymphonix Proxy with Automatically Detect Settings turned on it still lags when I first open a new IE window or tab.  
The PC I am running now is a realiively new PC and was not around when we were using the ISA server so this PC never used that configuration. I assume it must be a routing issue on this VLAN / subnet or a misconfiguration in my DNS.
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jtokarchukCommented:
I would check your VLAN over. I tend to agree that it is a routing issue.

I wouldn't say DNS because when IE is automatically detecting, it tends not to care if there are forward/reverse lookups for your proxy server. And if it were the case, (assuming you have one DC) it would be happening on all of your machines.
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AIC-AdminAuthor Commented:
After digging through some Wireshark packet captures I can see that my browser is sending out TCP Packets to "isa.ahc.net" which is our old ISA server / proxy which is no longer on the network.
My system is sending a TCP protocol with the following info "59782 > http [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=2]".
Somewhere on my network my PC is being told to send standard query requests to ISA.ahc.net instead of DC.ahc.net. After retrying about a dozen times to send requests to ISA.ahc.net my system finally sends its dns request to my domain controller which processes the request.
Any idea's where I can look to see where my PC is picking up the setting to send queries to my no existent ISA server? Also its worth noting that we got rid of our ISA server month before I purchased my current PC so my PC that is sending requests to ISA has never had any direct communication with that device.
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AIC-AdminAuthor Commented:
after researching I found the solution
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