Thankfully, Wireshark allows the user to quickly filter all that data, so you only see the parts you’re interested in, like a certain IP source or destination. Capturing so many packets, means that you will end up seeing huge captured files. Unfortunately, the amount of information you will get when capturing a network line can be daunting. One of the most used network protocol analyzer out there, it analyzes the files that come out of your network TAP (called also a packet capture device) or your computer’s NIC and lets you have an in-depth look into their parameters, messages, format, etc. This is where a tool like Wireshark comes in handy. The display filter syntax to filter out addresses between 192.168.1.1 – 192.168.1.255 would be ip.addr=192.168.1.0/24 and if you are comfortable with IP subnetting, you can alter the /24 to change the range.Most of the times, when your network crashes or you come across an issue, you have to search through your captured packets to find the problem. However, if the addresses are contiguous or in the same subnet, you might be able to get away with a subnet filter. One time-consuming approach would be to literally type out all the addresses you want to filter on. In this video, I respond to a question from one of my readers who wanted to create a display filter for many IP addresses. In either case, you will need to use a display filter to narrow the traffic down. Even when you have a capture filter, it may be too generic.
You may not know what to focus on when you capture packets, resulting in no capture filter.
A display filter is configured after you have captured your packets. A capture filter is configured prior to starting your capture and affects what packets are captured. Note that in Wireshark, display and capture filter syntax are completely different. In this video, I review the two most common filters in Wireshark. One of the keys to being an effective network troubleshooter when using a protocol analyzer is the ability to see patterns, which is where filters come into play.
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