Using Wireshark To Hunt for HTTP Errors

In this video, Tony Fortunato shows how to use the network protocol analyzer to troubleshoot a webpage error.

Tony Fortunato

June 7, 2016

1 Min Read
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One of the biggest advantages of using a network analysis tool with a reporting facility is the ability to aggregate and summarize specific characteristics to save you time and brain cells. For example, Wireshark has a lot of information you can reference or leverage when troubleshooting or baselining.

To demonstrate this, I'll show you how I recently resolved a problem a client was having trying to trace a webpage error. Using Wireshark, engineers at the customer site went to Statistics-> HTTP-> Packet Counters and did not see any errors even though they could obviously see an error clearly referenced on their screen. I explained that in this case, the word "error" needs to be properly explained.

Wireshark reports errors from a HTTP protocol perspective, but unfortunately their issue was that there was an actual webpage displayed with the error message. This can get a bit confusing, but as far as HTTP is concerned, the error page being returned is a valid page, therefore no error is reported.

The best analogy I can provide is when the mailman delivers you an overdue bill, he doesn’t know the details or situation, all he knows is that he delivered the mail.

I explained they need to dig deeper to find the error, and started with a protocol filter (HTTP).  After I found the packet with the error message, I leveraged a specific Display Filter to save time.

The client had originally suggested using the Find feature with the String/Bytes option. I agreed that would work, but it would be much easier if they could use a Display Filter so the only packets remaining on the screen are the offending packets.

About the Author(s)

Tony Fortunato

Sr Network Performance Specialist

Tony Fortunato is a network performance expert who has been designing, implementing and troubleshooting networks since 1989. His company, The Technology Firm, provides clients of all sizes with services ranging from project management, network design, consulting, troubleshooting, designing custom-designed training courses, and assisting with equipment installation. Tony's experience in networking started with financial trading floor networks and ISPs, where he learned to integrate and support equipment from various vendors. Tony has taught and presented at numerous colleges and universities, public forums and private classes. He blogs frequently at NetworkDataPediaand has a popular YouTube channel.

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