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TMG proxy issue

Posted on 2012-04-12
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Last Modified: 2012-05-16
Hi Experts-

We are having a problem regarding TMG proxy wpad.dat issue....

Every now and then (no particullar pattern) browsers are trying to connect to proxy using TMG RRAS ip addresses and then being blocked.

Opening a new browser window will use correct fqdn for TMG and internet access i OK.

We have run the  CarpNameSystem.js on TMG server.

Any ideas why this happens on and off?

Thanks
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Question by:jakobmarkussen
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LVL 3

Expert Comment

by:Dhanesh Kansari
ID: 37836786
Hi There,

cscript carpnamesystem.js /set:DNS

It sets proxy address in the wpad.dat to FQDN instead of IP (which in our case is a RRAS one). you can get code of this file from link given below.

http://isatools.org/tools/carpnamesystem.js
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Author Comment

by:jakobmarkussen
ID: 37836795
Hi. Thanks - didn't make it clear: That has been done.
If I run it again I just get a "nothing to correct" message.

I also tried running del /wpad*.dat /s on clients - that doesn't help.
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Expert Comment

by:Dhanesh Kansari
ID: 37836915
Hi There,

When you set up the internal network, did you enter the IP addresses in manually or did you use the "add adapter" button?

What is your network topology on the TMG 2010 server, Single Network Adapter or Edge Firewall?  

What IP address and subnet mask are on the external network?
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Expert Comment

by:Dhanesh Kansari
ID: 37836920
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Author Comment

by:jakobmarkussen
ID: 37836974
I will look at the link thanks.

Internal network I added adapter
It's Edge firewall
External adaptor has a couple of Public IP's
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LVL 10

Expert Comment

by:simonlimon
ID: 37841899
How is the wpad entry in the dns defined? Is it a CNAME or is it an A record. It could be possible that TMG would register its RRAS Ip's with the DNS...
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Author Comment

by:jakobmarkussen
ID: 37849974
I haven't a wpad dns entry.. Using DHCP.
Also no RRAS Ip's are in DNS.
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Author Comment

by:jakobmarkussen
ID: 37879851
Ok - found that in Routing and remote Access the DHCP Relay Agent has the IP address that is given to the wpad clients. how can we 'stop' this ? thx
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Accepted Solution

by:
simonlimon earned 500 total points
ID: 37879881
Remove it from the Scope options on the DHCP server for that network.

But if I were you, I would investigate why it was there in the first place.
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Author Comment

by:jakobmarkussen
ID: 37879903
Not sure what to remove.. Sorry...

The TMG was setup like this at some point: http://www.isaserver.org/img/upl/vpnkitbeta2/dhcprelay.htm

When using the internal dhcp for vpn clients - I will need relay agent, right?

Thanks
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Expert Comment

by:simonlimon
ID: 37879922
Go to the DHCP console, find the RRAS network, expand it, click on "Scope Options"

Find the 252 Option - WPad, then modify it or remove it. on the right screen.

New clients in that network will not get the WPAD IP.

Also make sure, that you consider possible consequences before performing this..
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Author Comment

by:jakobmarkussen
ID: 37880135
We might need a major clean up ;)

We do not have a dedicated RRAS network - RRAS is using the interal adapter on TMG so also using the same scope as internal ...

Perhaps we would be better of using dns for auto disc?
Only thing here is that we have more sites with seperates TMG's sharing DNS ... So we would need to figure out how to force clients on each site to use correct TMG /wpad setting...
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Author Comment

by:jakobmarkussen
ID: 37880706
Okay - I removed 252 option from DHCP- fwctool testautodetect no longer find wpad in DHCP.
I set up DNS instead. Thing was fine for an hpur or two.. Now I once againt get the same error.
Any idead why this is happing when using DNS to distr. autodiscover settings?
Thanks
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LVL 10

Expert Comment

by:simonlimon
ID: 37880809
Does this happen on all machines, or just a set of machines?

What is the exact symptom, Are you using a Load Balanced TMG - Enterprise?
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Author Comment

by:jakobmarkussen
ID: 37880842
At the moment just 2 machines. One Windows 7 and one XP. I worried that more machines might start to fail.

The thing starts suddenly. Internet browsing might be fine for hours, then suddenly we get this error that TMG denies connection. We see that it replies on rras relay agent IP.
Opening a new browser window and it works again.

Not load Balanced - and Standard TMG
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Expert Comment

by:simonlimon
ID: 37880899
If you monitoring the TMG traffic to and from that client, what do you see in that interval?
TMG console , Logs and reports, logging - check the traffic in the last hour ..
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Author Comment

by:jakobmarkussen
ID: 37880918
I will setup logging for one of the machines tomorrow morning to se what happens around failure.. thx

I have attached a rras info on TMG.
Perhaps the issue make more sence then?
rras.png
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Author Comment

by:jakobmarkussen
ID: 37884800
So it just happened.
Was browsing normally untill suddenly TMG denied access:

Technical Information (for support personnel)
Error Code: 403 Forbidden. Forefront TMG denied the specified Uniform Resource Locator (URL). (12202)
IP Address: 10.45.205.188
Date: 4/24/2012 6:32:41 AM [GMT]
Server: xx.yy.zzz
Source: proxy

Where 10.45.205.188 is rras ip ...

TMG log show nothing - normal traffic to TMG server IP - then it starts trying to use 10.45.205.188 as proxy out of nowhere.
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Expert Comment

by:simonlimon
ID: 37885521
What is in your WPAD entry for DNS? Hostname or IP?
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Author Comment

by:jakobmarkussen
ID: 37885688
It was Hostname - I have changed to IP - will check if that changes anything
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Author Comment

by:jakobmarkussen
ID: 37885697
Changing it to IP causes autodetect to fail...
0
 
LVL 10

Expert Comment

by:simonlimon
ID: 37906206
You changed to one of TMGs IPs?

It doesn't really make sense it would fail, because the hostname points to the same IP?

Do the clients receive the Wpad.dat file from the TMG?

You can check this by entering http://xx.yyy.xxx.zzz/wpad.dat, where xx.yyy.xxx.zzz is the IP you changed it to.

And then monitor this from the TMG console.

Also if you do a Nslookup in your environment, how does it resolve this hostname?
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Author Comment

by:jakobmarkussen
ID: 37913404
Yes the clients recieve wpad from TMG.
I tried to change to IP number instead of fqdn .. Let's see if that is changing anything.

Thanks so far
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Author Comment

by:jakobmarkussen
ID: 37917953
Lasted almost 24h. This morning wpad IP changed again for the affected clients.
This is driving me crazy :)
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Author Comment

by:jakobmarkussen
ID: 37918230
Restartet computer and the problem returned.
If I open another IE windows wpad is fine.
The IE window with "the wrong wpad IP" is still not getting the right IP..

nslookup is fine..

Thx
0
 
LVL 10

Expert Comment

by:simonlimon
ID: 37919132
This may be a long shot, but can you try opening the wpad.dat that you download from a browser and check whether this IP is referenced in it?

Do the problematic clients have any entries in their hosts file?
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Author Closing Comment

by:jakobmarkussen
ID: 37974052
Hi Simon - been on vacation so haven't been able to update this untill now.
The last 2 days no clients have failed.
I'll accept your answers as solutions - but can't tell what did the trick.
Thanks for helping out - will "re-open" if the problem returns.
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