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The generic format of an Ethernet frame is defined below, the 'options' fields may be present if the Type/Length field indicates a VLAN TPID. The VLAN extended Frame Format is defined here and the MAC format here.
|Preamble||Destination MAC||Source MAC||Type/Length||Options||Data||FCS|
|8||6||6||2||?||46 - 1500||4|
|64 - 1518 bytes|
The MAC address (aka EU-48) is an IEEE 802 administered format consisting of 48 bits:
Note: Bits are numbered 1 to 48 starting on left using the standard IETF convention. IEEE uses a 1 - 8 bit per byte notation with 1 on the RIGHT.
|Organizationally Unique Id (OUI) 24 bits (3 octets)||Unique Interface Value 24 bits (3 octets)|
|Unique value assigned to an organization by IEEE (aka Vendor ID). The top (leftmost) octet has the following format:
|Unique Address assigned by OUI (vendor) if bit 7 (U/L) of first MAC octet is 0 or local administrator if bit 7 (U/L) of first MAC octet is 1.|
Note: When the MAC is used to construct an IPv6 EUI-64 address using Stateless configuration the meaning and values of the U/L (bit 7) are reversed.
The VLAN Extension is PRESENT if the the value of the first Type/Length field is x'8100 (TPID - Tag Protocol Identifier). The Frame Type/Length value is then replaced with the extended VLAN frame as defined below.
|2||2||?||2||46 - 1500|
The TCI is a 16 bit value defined as follows:
|user_priority||CFI||12 bit VID (VLAN ID)|
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Dec > Hex > Bin
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