(XXX - add a list of system that supply the FCS and the systems that don't?) This can be confusing as the FCS is often not shown by Wireshark, simply because the underlying mechanisms simply don't supply it. Allowed Packet LengthsĮthernet packets with less than the minimum 64 bytes for an Ethernet packet (header + user data + FCS) are padded to 64 bytes, which means that if there's less than 64-(14+4) = 46 bytes of user data, extra padding data is added to the packet.īeware: the minimum Ethernet packet size is commonly mentioned at 64 bytes, which is including the FCS.
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. Packet formatĪ physical Ethernet packet will look like this: PreambleĪs the Ethernet hardware filters the preamble, it is not given to Wireshark or any other application. Information how to capture on an Ethernet network can be found at the CaptureSetup/Ethernet page. You can find hardware related Ethernet information at the EthernetHardware page. It is specified by various IEEE 802.3 specifications.Įthernet sends network packets from the sending host to one ( Unicast) or more ( Multicast/ Broadcast) receiving hosts.
Ethernet is the most common local area networking technology, and, with gigabit and 10 gigabit Ethernet, is also being used for metropolitan-area and wide-area networking.
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