3Com Switch 4800G 24-Port - Vlan C; Introduction to VLAN

9
VLAN CONFIGURATION
When configuring VLAN, go to these sections for information you are interested
in:
■ “Introduction to VLAN” on page 83
■ “Configuring Basic VLAN Attributes” on page 86
■ “Basic VLAN Interface Configuration” on page 86
■ “Port-Based VLAN Configuration” on page 87
■ “MAC Address-Based VLAN Configuration” on page 91
■ “Protocol-Based VLAN Configuration” on page 92
■ “Configuring IP-Subnet-Based VLAN” on page 94
■ “Displaying and Maintaining VLAN” on page 95
■ “VLAN Configuration Example” on page 95
Introduction to VLAN
VLAN Overview Ethernet is a network technology based on the Carrier Sense Multiple
Access/Collision Detect (CSMA/CD) mechanism. As the medium is shared in an
Ethernet, network performance may degrade as the number of hosts on the
network is increasing. If the number of the hosts in the network reaches a certain
level, problems caused by collisions, broadcasts, and so on emerge, which may
cause the network operating improperly. In addition to the function that
suppresses collisions (which can also be achieved by interconnecting LANs), virtual
LAN (VLAN) can also isolate broadcast packets. VLAN divides a LAN into multiple
logical LANs with each being a broadcast domain. Hosts in the same VLAN can
communicate with each other like in a LAN. However, hosts from different VLANs
cannot communicate directly. In this way, broadcast packets are confined to a
single VLAN, as illustrated in the following figure.