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According to wikipedia, ethernet frame is 1522 bytes long. However, in wireshark's wiki, it seems it is not always true:

As the Ethernet hardware filters the preamble, it is not given to Wireshark or any other application. Most Ethernet interfaces also either don't supply the FCS to Wireshark or other applications, or aren't configured by their driver to do so; therefore, Wireshark will typically only be given the green fields, although on some platforms, with some interfaces, the FCS will be supplied on incoming packets.

Questions:
1. Is the length of ethernet fixed between all hardware?
2. How to know the length of ethernet frames in linux?

user762750
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  • In short, the length of ethernet frames isn't fixed, each frame has a different length. The hardware tells the OS how long each particular frame is, so whatever packet sniffing tool you are using (e.g., wireshark) should pass that information on to you. – Harry Johnston Jul 13 '19 at 09:04
  • @HarryJohnston Thanks for the reply, what’s the command to find out the frame length by wireshark? – user762750 Jul 13 '19 at 09:12
  • If you're using the GUI, [it would appear that the packet length is displayed fairly prominently.](https://www.wireshark.org/docs/wsug_html_chunked/ChapterIntroduction.html#ChIntroFig1) – Harry Johnston Jul 13 '19 at 23:45
  • Ethernet frames can be examed by wireshark using `tshark -i -O ether` command – user762750 Jul 16 '19 at 09:47

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