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Archive for August, 2013

Some Quick Troubleshooting with IE Developer Debug Tools

Posted by William Diaz on August 29, 2013


I probably spent too much time trying to figure this one out, especially considering I have used the IE Developer Tools (F12) to troubleshoot IE issues in the past, and the fix would have been amazingly fast if I had employed this resource at first. The problem was that a user was unable to view patent images from a website. In the past, this site had used different file formats to send the pages to the browser, such as TIFF. However, regardless of the TIFF viewer application installed, the pages would not render in the browser. Instead there was a red x displayed indicating the image could not be loaded.

After about half an hour of troubleshooting, I went to F12, selected the Script tab in the Developer tools to see what the javascript wanted to do and saw my answer near the bottom of the script:

image

The webpage was not trying to deliver a TIFF file. Instead, it was wanted to send a PDF. The fix? Change the PDF application (Adobe in this case) to display PDFs in the browser. I also should have avoided listening to the user insisting that the problem was with TIFFs.

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Java 7 Domain Account Locks

Posted by William Diaz on August 16, 2013


We recently moved from Java 6 to Java 7, specifically JRE 7 Update 25. Immediately, we began get reports of user accounts getting locked after the affected users visited web sites hosting Java applets. For the most parts, the applets would run until the 5th attempt to load-refresh the applet and then the domain account would get locked. The initial look with Network Monitor showed that authenticated users were failing at the proxy level:

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The spot-workaround was to create bypass rules for the individual sites to allow all users to pass without authentication, which was by no means a elegant since it was a reactionary approach  that waited for user’s to get locked across various offices and then report the problem to tier 1 and then escalate.

When the support issues began to settle down, I began to look more deeply into the problem. We took a non-production proxy and removed all the rules that were created over the previous days so that any Java applet would begin failing authentication (I used the Java Verify page as my test). I have to admit, network traffic and protocols are not my Zen, but as I began to look at various captures and figure may way around netmon, I saw the same theme each time, Kerberos authentication failing:

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A Little Netmon Goes a Long Way

Posted by William Diaz on August 13, 2013


You don’t necessarily need to be a network guru to use Microsoft Network Monitor. I have used it more than a few times to troubleshoot client side applications that fail to connect to external resources for whatever reason. For example, a user unable to logon to a some external server, receiving the follow error: “The remote server returned an error: (502) Bade Gateway

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I tried the site myself with Netmon capturing a trace and saw the remote server was trying to establish a secure connection through a port other than common 443:

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And here where printing from a remote app was failing to pass through our TMG proxy:

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