Vlan Overview; Vlan C Onfiguration - 3Com 4200G 12-Port Configuration Manual

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VLAN Overview

Introduction to VLAN
VLAN C
ONFIGURATION
The virtual local area network (VLAN) technology is developed for switches to control
broadcast operations in LANs.
By creating VLANs in a physical LAN, you can divide the LAN into multiple logical
LANs, each of which has a broadcast domain of its own. Hosts in the same VLAN
communicate with each other as if they are in a LAN. However, hosts in different
VLANs cannot communicate with each other directly. Figure 19 illustrates a VLAN
implementation.
Figure 19 A VLAN implementation
LAN Switch
A VLAN can span across multiple switches, or even routers. This enables hosts in a
VLAN to be dispersed in a more loose way. That is, hosts in a VLAN can belong to
different physical network segment.
VLAN enjoys the following advantages.
1 Broadcasts are confined to VLANs. This decreases bandwidth utilization and improves
network performance.
2 Network security is improved. VLANs cannot communicate with each other directly.
That is, hosts in different VLANs cannot communicate with each other directly. To
enable communications between different VLANs, network devices operating on
Layer 3 (such as routers or Layer 3 switches) are needed.
3 Configuration workload is reduced. VLAN can be used to group specific hosts. When
the physical position of a host changes, no additional network configuration is
required if the host still belongs to the same VLAN.
VLAN standard is described in IEEE 802.1Q, which is issued by IEEE in 1999.
VLAN A
VLAN B
LAN Switch
VLAN A
VLAN B
Router
VLAN A
VLAN B