Confused about the header size for a Ethernet frame
A regular 802.3/Eth-II ethernet frame doesn't carry VLAN info.
802.1Q can carry VLAN (and QoS) info over to the receiving end.
If the ethertype is 0x8100 then you got yourself an 802.1Q tag which is another 4 bytes in addition to the 14 bytes (dmac+smac+type).
See wikipedia for reference. http://en.wikipedia.org/wiki/Ethernet_frame
EDIT:
Regular Eth-II/802.3 has a total length of:
dmac(6)+smac(6)+etype(2)+payload(1500)+crc(4) = 1518 bytes
For the case of Eth-II/802.3 with 802.1Q tagging:
dmac(6)+smac(6)+8100(2)+vlan/Qos(2)+etype(2)+payload(1500)+crc(4) = 1522 bytes
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Updated on June 04, 2022Comments
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Bic B almost 2 years
I was researching a few things about
VLANs
and came across theVLAN tag
and also the headers.If we have a MTU for a standard
802.3 Ethernet frame
(1518 bytes) what is included in the header802.3
?Also how do we calculate the header length for that?
What is the difference between
802.3 and 802.1q
? I know that the VLAN tag requires extra bytes but how to calculate how many bytes needed to the802.1q VLAN tag
?Thanks in advance
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Bic B over 11 yearsso what will be the total length for 802.3?