B
Virtual LANs (VLANs)
B.1 VLANs AND FRAME TAGGING
The switch supports IEEE 802.1Q-compliant virtual LANs (VLANs). This capability provides a highly efficient architecture for establishing VLANs within a network and for controlling broadcast/multicast traffic between workgroups. Central to this capability is an explicit frame tagging approach for carrying VLAN information between interconnected network devices.
With frame tagging, a four-byte data tag field is appended to frames that cross the network. The tag identifies which VLAN the frame belongs to. The tag may be added to the frame by the end station itself or by a network device, such as a switch. In addition to VLAN information, the relative priority of the frame in the network can be specified by the tag. For more information, refer to (Appendix D).
VLANs provide greater network efficiency by reducing broadcast traffic, but also allow you to make network changes without having to update IP addresses or IP subnets. VLANs inherently provide a high level of network security, since traffic must pass through a Layer 3 switch or a router to reach a different VLAN.
This switch supports the following VLAN features:
•Up to 1024 VLANs based on the IEEE 802.3Q standard
•Port overlapping, allowing a port to participate in multiple VLANs
•End stations can belong to multiple VLANs
•Passing traffic between VLAN-aware and VLAN-unaware devices
•Two-level priority tagging
•Port trunking with VLANs
