3Com Switch 8800 Advanced Software V5 Configuration Guide

14
VLAN CONFIGURATION
When configuring VLAN, go to these sections for information you are interested
in:
■ “Introduction to VLAN” on page 155
■ “Configuring Basic VLAN Attributes” on page 157
■ “Configuring VLAN Interface Basic Attributes” on page 157
■ “Configuring the Port-Based VLAN” on page 158
■ “Configuring the Protocol-Based VLAN” on page 161
■ “Displaying and Maintaining VLAN” on page 163
■ “VLAN Configuration Examples” on page 163
Introduction to VLAN
VLAN Overview The communication medium is shared in Ethernet. If the number of the hosts in
the network reaches a certain level, problems caused by collisions, broadcasts, and
so on emerge, resulting in improper network operation. Interconnecting LANs can
suppress collisions but cannot isolate broadcast packets. Therefore, VLAN (virtual
LAN) is developed to solve these problems. 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.
Figure 43 A VLAN diagram
VLAN 2
VLAN 5
Switch BSwitch A
Router