Wireshark-users: [Wireshark-users] Checksum Display Filters
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From: "Keith French" <keithfrench@xxxxxxxxxxxxx>
Date: Sun, 11 Feb 2007 20:20:00 -0000
In the IP, TCP or UDP headers is the "Checksum" field, which has two parts to it. For the IP checksum this is:-
 
Header checksum: 0xbbd5 [correct]
        [Good: True]
        [Bad : False]
 
with similar for the TCP and UDP checksums.
 
Is there any difference from a logical point of view when using a display filter to find packets with bad IP checksums between these two expressions:-
 
ip.checksum_bad == 1
 
or
 
ip.checksum_good == 0
 
As a checksum can only be correct or bad, surely both of these filters are the same?