VLAN Management
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802.1Q VLAN
The VLAN interworking of different manufacturers’ equipment is ensured by the 802.1Q
standard issued by IEEE in 1999 for defining the VLAN international standard.
As required in 802.1Q protocol, one 4 bytes 802.1Q VLAN tab is bound to be wrapped
behind the destination MAC address and the source MAC address of the Ethernet frame for
identifying the relevant information of VLAN. As shown below, the Ethernet frame with
802.1Q tag is produced by adding an 802.1Q VLAN tag behind the destination MAC
address and the source MAC address of the standard Ethernet frame.
The information in the 802.1Q tag is specified as following:
Field
Specification
TPID
Identify the data frame with the 802.1Q VLAN Tag. This field’s length is 2 bytes,
means 16 bit. The IEEE 802.1Q protocol defines the value of it to be 0x8100.
Priority
Identify the priority of data frame and send the high priority data packets in
advance when the switch is blocked.
The value range of this 3 bits field is <0~7> with 7 displaying the highest priority
and 0 the lowest.
CFI
Identify whether the MAC address is wrapped in a standard format. The field
length is 1 bit.
The standard format wrap of MAC address is indicated by 0, otherwise by 1.
The default value of the Ethernet switch is 0.
