When troubleshooting a network problem, you don't always end up with one convenient Wireshark capture file. Sometimes you have multiple packet captures taken from different interfaces, different locations, or different points in time. Instead of opening each file separately and trying to piece everything together, Wireshark can merge multiple capture files into a single file. This can make analyzing a complicated network problem considerably easier, especially when you need to compare traffic from multiple sources.
There are several ways to merge Wireshark capture files, and the option you choose depends on what you are trying to accomplish. Wireshark's File → Merge function allows you to combine another capture with the capture you currently have open. You can prepend packets, append packets, or merge the packets chronologically. Wireshark also supports merging capture files by dragging multiple files into the application, while the command-line mergecap utility provides additional options for more advanced workflows.
The chronological option is particularly useful when captures were taken at the same time from different interfaces or locations. Instead of simply putting one capture after another, Wireshark can organize the packets according to their timestamps. This can make it much easier to follow a conversation and understand what was happening across different parts of the network. For example, if you're troubleshooting a client-to-server communication problem and have captures from both ends of the connection, combining the captures can give you a much more complete picture of the traffic.
Another useful option is mergecap, the command-line tool included with Wireshark. It is particularly handy when you regularly work with multiple capture files or need to automate packet-capture processing. Wireshark's documentation notes that mergecap provides more options than the graphical merge function, making it a useful tool for technicians who work with larger or more complicated packet-capture investigations.
In the accompanying video, I demonstrate the process of merging Wireshark capture files and show why this can be a useful technique when analyzing network traffic. If you've ever ended up with several PCAP or PCAPNG files and wondered how to turn them into one capture that is easier to analyze, this is a simple Wireshark feature worth knowing. You can read the original article on LoveMyTool and watch the video for the practical demonstration. Sometimes the hardest part of network troubleshooting isn't capturing the packets—it's getting all those packets into one place so you can actually see what is happening.
This one is simple, 2 ways to merge Wireshark trace files.