Black Box LB522A-KIT, Руководство пользователя

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Black Box DeeSL.2 Ethernet Extender
The Tag Control Information (TCI) section of a VLAN tag includes information on the
user Priority level, the Canonical Format Indicator (CFI) and VLAN ID (VID).
• Tag Protocol Identifier (TPID) is a defined value of 8100 in hex. When a frame
has the EtherType equal to 8100, this frame carries the tag IEEE 802.1Q /
802.1P.
• Priority defines the priority level for different classes of traffic. There are 8 possi-
ble priority levels, with 0 being the lowest priority level and 7 being the highest
level. IEEE 802.1P defines the operation for these 3 user priority bits.
• Canonical Format Indicator (CFI) is always set to zero for Ethernet switches.
CFI is used for compatibility reasons between an Ethernet-type network and
Token Ring-type network. If a frame received at an Ethernet port has a CFI set to
1, then that frame should not be forwarded as it is to an untagged port.
• VLAN ID (VID) is the unique identification number of the VLAN, which is used by
the standard 802.1Q. It has 12 bits and allows the identification of 4096 (212)
VLANs. Of the 4096 possible VIDs, a VID of 0 is used to identify priority frames
and the value 4095 (FFF) is reserved, so the maximum possible VLAN configu-
rations are 4,094.
The LB52xA-KIT initially configures one VLAN by default, VID=1. A port such as
LAN1–4, line or sniffing can have only one Port VID (PVID), but can have as many VID
groups as the LB52xA-KIT has memory in its VLAN table to store them.
Ports in the same VLAN group share the same frame broadcast domain thus increase
network performance through reduced broadcast traffic. You can modify VLAN groups
at any time by adding, moving or changing ports without any re-cabling.