3Com 4.2.2 manual Vlan Type 3Com Product

An Introduction to ATM and VLAN Management Basics C-7

In practice, it is not the individual LAN stations that are formed into VLANs but rather the physical Ethernet LANs, called Ethernet segments, that are grouped into VLANs. Thus, all stations on an Ethernet segment will be on the same VLAN. Also, since an Ethernet segment is connected to the network through an Ethernet port in an edge device, the Ethernet port itself is sometimes referred to as a member of the VLAN.

Advantages A Virtual LAN, as opposed to an Ethernet LAN, has the great advantage of being very easy to manage from a central location. Stations are added or removed from Virtual LANs by software without regard to their location, there is no need to change physical connections.

The organization of the network into VLANs also reduces congestion from broadcast frame transmissions. Broadcast frames are now sent only to members of the same VLAN instead of to all stations on the network.

Virtual LANs also offer network security for their members. Because transmissions do not normally cross from one VLAN to another, a VLAN will remain immune to transmission problems or congestion that may occur in another VLAN in the network.

VLAN Types According to the enabling technology, VLANs are divided into three types: ATM-basedVLANs, tag-basedVLANs and protocol-basedVLANs. In the following sections each of these VLAN types is discussed. These Virtual LAN types are implemented in 3Com products as follows:

Table B-1VLAN Types in 3Com products

VLAN Type	3Com Product
ATM-based	CoreBuilder 7000
	CoreBuilder 7X00
	SuperStack II Switch 2700
	CoreBuilder 5000
	SwitchModule
Tag-based	SuperStack II Switch
	1000/3000
Protocol-based	CoreBuilder 2500/6000

These three VLAN types are discussed in the following sections.