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I am not able to find the correct/wrong "frame check sequence" in wireshark v3.0.2. All it show is [unverified]. How do i find the wlan.fcs.status==1 in this version?

asked 2019-11-07 06:46:29 +0000

Sujith gravatar image

updated 2019-11-07 11:29:22 +0000

I am using Wireshark v3.0.2 edition where i am not able to find the correct/incorrect FCS status under the Frame Control Field whereas it show [unverified]. Earlier edition of wireshark used to display the correct/incorrect sequence. Incorrect sequence relates to some kind of a checksum error. All i spot now is some malformed packets but incorrect frame sequence. Can someone help me to figure this out?

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Can you check the display filter name you reference? I can't find fcs.status in the Field Reference Guide.

grahamb gravatar imagegrahamb ( 2019-11-07 10:43:21 +0000 )edit

Thank you. I figure out the status from edit->preferences->Advanced->Search for wlan.check_checksum. Earlier it was in False, now i have changed it to TRUE by double-clicking on it. Now if search for wlan.fcs.status==1, it displays all the "Good" FCS.

Sujith gravatar imageSujith ( 2019-11-07 11:29:04 +0000 )edit

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answered 2019-11-07 13:04:44 +0000

grahamb gravatar image

From the 3.0 Release notes:

The Ethernet and IEEE 802.11 dissectors no longer validate the frame check sequence (checksum) by default.

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Any idea why is it so. I thought it contributes to the analysis while checking for Network Traffic issues.

Sujith gravatar imageSujith ( 2019-11-07 13:17:44 +0000 )edit

Due to checksum offloading by NIC's the FCS is often inaccurate so change 28477 disabled by default it for Ethernet. Subsequently change 28485 disabled it by default for 802.11 so that it was consistent with other places in the code.

grahamb gravatar imagegrahamb ( 2019-11-07 13:51:16 +0000 )edit

Thank you. That was very helpful.

Sujith gravatar imageSujith ( 2019-11-07 14:12:51 +0000 )edit

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Asked: 2019-11-07 06:46:29 +0000

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Last updated: Nov 07 '19