Enterasys Networks 802.1Q - Manual (Page 14)

VLAN Terms
1-4 Virtual Local Area Networks
1.4 VLAN TERMS
To fully understand the operation and configuration of port based VLANs, it is essential to
understand the definitions of several key terms.
VLAN ID
A unique number (between 1 and 4094) that identifies a particular VLAN.
VLAN Name
A 32-character alphanumeric name associated with a VLAN ID. The VLAN Name is intended to
make user-defined VLANs easier to identify and remember.
Filtering Database Identifier (FID)
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 FID 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 FID that matches its VLAN ID.
Tag Header (VLAN Tag)
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.
Tagged Frame
A data frame that contains a Tag Header. A VLAN aware device can add the Tag Header to any
frame it transmits.
Untagged Frame
A data frame that does not have a Tag Header.
Default VLAN
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.
Forwarding List
A list of the ports on a particular device that are eligible to transmit frames for a selected VLAN.