D-Link DES-3250TG User Manual page 43

DES-3250TG Layer 2 Fast Ethernet Switch User's Guide
The tag is inserted into the packet header making the entire
packet longer by four octets. All of the information contained in
the packet originally is retained.
Figure 5- 4. IEEE 802.1Q Tag
The EtherType and VLAN ID are inserted after the MAC source
address, but before the original EtherType/Length or Logical
Link Control. Because the packet is now a bit longer than it
was originally, the Cyclic Redundancy Check (CRC) must be
recalculated.
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