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APPENDIX B. VIRTUAL LANS (VLANS)
VLANs and Frame Tagging
The
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 specified by the tag (see Appendix C, “Class of Service”).
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 256 VLANs based on the IEEE 802.1Q standard
•Distributed VLAN learning across multiple switches using explicit or implicit tagging and GARP/GVRP protocol
•Port overlapping, allowing a port to participate in multiple VLANs
•End stations can belong to multiple VLANs
•Passing traffic between
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•Port trunking with VLANs
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