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Table 12-1 VLAN Terms and Definitions (Continued)
VLAN Term
Filtering Database
Identifier (FDB ID)
Tag Header (VLAN Tag)
Tagged Frame
Untagged Frame
Default VLAN
Forwarding List
Port VLAN List
Filtering Database
Definition
Addressing information that the device learns about a VLAN is
stored in the filtering database assigned to that VLAN. Several
VLANs can be assigned to the same FDB ID to allow those
VLANs to share addressing information. This enables the devices
in the different VLANs to communicate with each other when the
individual ports have been configured to allow communication to
occur.
The configuration is accomplished using the Local Management
VLAN Forwarding Configuration screen. By default a VLAN is
assigned to the FDB ID that matches its VLAN ID.
Four bytes of data inserted in a frame that identifies the
VLAN/frame classification. The Tag Header is inserted into the
frame directly after the Source MAC address field. Twelve bits of
the Tag Header represent the VLAN ID. The remaining bits are
other control information.
A data frame that contains a Tag Header. A VLAN-aware device
can add the Tag Header to any frame it transmits.
A data frame that does not have a Tag Header.
The VLAN to which all ports are assigned upon initialization.
The Default VLAN has a VLAN ID of 1 and cannot be deleted or
renamed.
A list of the ports on a particular device that are eligible to
transmit frames for a selected VLAN.
A per port list of all eligible VLANs whose frames can be
forwarded out one specific port and the frame format (tagged or
untagged) of transmissions for that port. The Port VLAN List
specifies what VLANs are associated with a single port for frame
transmission purposes.
A database structure within the switch that keeps track of the
associations between MAC addresses, VLANs, and interface
(port) numbers. The Filtering Database is referred to when a
switch makes a forwarding decision on a frame.
VLAN Operation and Network Applications
VLAN Terms
12-5
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