I have attended multiple Wireshark webinars presented by Riverbed and leaders in the field. They title this series “Return to the Packet Trenches” with some sort of variation or subtitle for the different sessions. I always walk away with something new. This latest webinar was no exception. It reviewed several CLI options for creating, analyzing, and editing packet captures. I highly recommend attending these webinars if you have any interest in Wireshark and staring at packets.

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The phrase, “I can’t access my shared drive” was intermittent, but becoming common for a remote location connected via an MPLS circuit. Without hesitation the finger was pointed at the network and my phone rang. People connect to shared drives everyday, but it is one of those things they take for granted. Behind the scenes there are many layers of technology, protocols, and devices working together to make those connections happen.

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As mentioned in this post, you can create and share custom profiles. However, that is not the extent of profile management. Another great way to utilize these files is to synchronize Wireshark profiles between systems. In this day and age you probably have more than one computer (laptop, VM, home desktop??). Also, if you’re like me you probably have Wireshark installed on anything you can get your hands on! It can be a bit of a pain to keep your favorite Wireshark settings such as protocol options, coloring rules, and saved display filters up to date with each Wireshark installation.

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As mentioned in this post, Wireshark is easy to customize and even provides the ability to share custom profiles. Just about everything that can be modified can be shared. I outlined several of those items in the linked post. Wireshark uses files to store the config items located in a couple of key places. The ones I have shared below are all contained in the “Personal configuration” directory. To get sharing right away follow these steps:

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One of the great things about Wireshark is the completely customizable interface. Users can change the layout, column settings, protocol decode options, add/remove buttons, change colors, add/remove filters, and more. There is a lot of documentation on how to even write new protocol dissectors. Due to its open source nature and the active development community, one can modify the code and/or participate in its official development. What this means is no two instances of a Wireshark install have to be the same.

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One of the most common problems any IT admin faces is a software update. While software updates are generally considered a good thing, because they patch security flaws, fix bugs, try to improve performance, and more, they are also a common source of problems. Every admin knows to be ready for calls after a scheduled maintenance window. This issue was no different.   A ticket came in stating users could not access a web app through the backend system after an upgrade to Java 1.

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Have you ever had a nightmare where you are being chased and you can’t just seem to run away fast enough? No? Well, maybe you’ve tried running through snow up to your knees or swimming while wearing jeans. All of those examples point to situations that feel like something isn’t quite right. Cases where there could be better performance if only something was changed or improved. Sometimes this same thing happens to network devices.

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I recently sat for the Wireshark Certified Network Analyst certification again. This will be the second time I have taken it and the second time I have passed. I have taken several various networking certification exams, networked with people who have sat for others, and read about many more. Keeping all of that in mind, I think this is one of the most straightforward certification tests I have seen. Laura Chappell, Gerald Combs, and the team have done a great job with the books and preparation materials.

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Using file sets in Wireshark is a great feature. It allows for quickly navigating between smaller files instead of experiencing sluggish performance when analyzing one large file. However, there are times when packet captures were taken using a system other than Wireshark (such as TCPDump or Dumpcap). Other times someone else performs the captures and uses a different naming convention. Either way, there are times when it would be nice to convert these names into Wireshark’s file set naming convention.

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Start the Capture Now that you’ve decided where to capture, and you’ve prepared your interfaces and filters, you are ready to perform the capture. All you have to do at this point is hit the start button or double-click the interface in the list. There are usually multiple interfaces listed, so make sure you know which one you are wanting to use. Generally, this may be indicated by a small moving graph to the right of the device name indicating there is traffic present (the screen shot below currently show no traffic as I was in a lull).

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Chris Sereno

For 11 years networking was my profession with a specialized focus on proactive and reactive performance analysis. More recently I have embraced the AWS platform. This blog reflects my experience both past and present.

AWS Architect at Caterpillar, Inc.

US