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Wireshark Filter explanations/guide

asked 2020-04-02 15:40:33 +0000

alohawireshark gravatar image

I am a data scientist analyzing packet data from Wireshark but I do not have a networking background. It's been a laborious process of Googling each filter from the tsharkoutput to build an intuitive understanding of each field, two fields just to illustrate my point: "ip.flags.rb" or "ip.flags." While the shorthand of such fields may have more meaning to an experienced network engineer, most is lost on me. I have reviewed the Wireshark documentation ( and the definitions are:

ip.flags            Flags   Unsigned integer, 2 bytes   1.0.0 to 3.2.2
ip.flags.rb Reserved bit    Boolean                     1.0.0 to 3.2.2

Such a definition doesn't answer critical questions like, "what is the range of integers for ip.flags and what would be the significance of each? Or, "what is the significance of a 1 for ip.flags.rb as opposed to a 0, i.e. why might it matter if a bit is reserved or not?"

My question is, is there a cheat sheet for newbies/non-network engineers with such information? Thus far, it seems like in-depth explanations can occasionally be found in the Wireshark documentation, albeit spread across many chapters. I can also find discussion of individual fields on forums/blogs, but with 273+ fields to try to understand, I'm wondering if there is a better resource I haven't yet found that is available.

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answered 2020-04-02 15:48:36 +0000

grahamb gravatar image

There is no further explanation of filter fields in Wireshark except the info in the source code attached to the creation of each filter field.

This info is available in the fields definition, and in the status bar if you click on a field in the packet details pane.

Each protocol will have the definitions of the fields in some sort of RFC or specification document (which may not be freely available) and the dissector developer will then name the filter fields as they see fit.

So, to find out the meaning of the filter fields, you need to go to the source definition of the protocol and hopefully the filter field names will tie up with the information there.

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tl;dr: Wireshark analyzes network traffic, so to understand what it's reporting requires some understanding of the protocols it's analyzing.

Guy Harris gravatar imageGuy Harris ( 2020-04-02 18:41:15 +0000 )edit

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Asked: 2020-04-02 15:40:33 +0000

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Last updated: Apr 02 '20