HP Network Direr Software Products manual 802.1Q VLANs, Ieee 802.1Q standard for VLANs aims to

502CHAPTER 13: VLAN MANAGEMENT

networks grow and the amount and types of traffic increase, bridge flooding may create unnecessary traffic problems that can clog the LAN. VLANs increase the efficiency of your network because each VLAN can be set up to contain only those devices that need to communicate with each other. With VLANs, if a bridge port receives a packet with a broadcast, multicast, or unknown destination address, the switch only forwards the packet to other ports in the same VLAN as the receiving port.

802.1Q VLANs

The IEEE 802.1Q standard for VLANs aims to:

■Define an architecture to logically partition bridged LANs and provide services to defined user groups, independent of physical location.

■Allow interoperability between multi-vendor equipment.

The 802.1Q standard allows each port on your switch to be placed in:

■Any VLAN defined on the switch.

■Several VLANs at the same time using 802.1Q tagging. The standard specifies a tag format that embeds VLAN membership information within each packet in a 12-bit VLAN ID (VID). This allows traffic from multiple VLANs to be carried across one physical link.

The standard requires that you define the following information about each VLAN on your switch before the switch can use it to forward traffic:

■VLAN Name — This is a descriptive name for the VLAN for example, Marketing or Management.

■802.1Q VLAN ID — This is used to identify the VLAN if you use 802.1Q tagging across your network. It can have a value from 1 to 4094, however VID 1 is reserved for the default VLAN. See “The Default VLAN” on page 504.

Port-based VLANs

A port-based VLAN is a collection of ports across one or more switches that are configured as members of the same VLAN. Devices attached to ports within the VLAN collection are members of the VLAN. In general, VLANs on 3Com switches are port-based VLANs and as a result VLAN support in 3Com Network Director is aimed at port-based VLANs.