Chapter 1: Virtual Local Area Networks
1.3BENEFITS AND RESTRICTIONS
The primary benefit of the 802.1Q VLAN technology is that it provides localization of traffic. This function also offers improvements in security and performance to stations assigned to a VLAN.
While the localization of traffic to VLANs can improve security and performance, it imposes some restrictions on network devices that participate in the VLAN. Through the use of Filtering Database ID’s (FIDs) security can be implemented to enable or prevent users from one or more VLANs from communicating with each other.
One or more VLANs can be assigned to a FID so that all the users that share a common FID can communicate with each other regardless of their VLAN affiliation. However, for the sake of security, the members of one FID cannot communicate with the members of another FID.
To set up a VLAN, all the network switch devices that are assigned to the VLAN must support the IEEE 802.1Q specification for VLANs. Before you attempt to implement a VLAN strategy, ensure that the switches under consideration support the IEEE 802.1Q specification.
1.4VLAN 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
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.
802.1Q VLAN User’s Guide |