Allied Telesis AT-S25 - Manual (Page 139)

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Appendix A
Introduction to Virtual LANs
A virtual LAN (VLAN) is a group of end nodes that function as if they are a
part of the same LAN segment. A VLAN can consist of end nodes located
in one specific area of a network or of end nodes that are widely
dispersed. This flexibility allows you to form logical workgroups of end
nodes located anywhere on your network.
A VLAN constitutes a broadcast domain. A VLAN restricts the
transmission of broadcasts only to the end nodes that are members of
the same VLAN. Members of a VLAN can communicate directly with
other members of the same VLAN. If an end node needs to communicate
with a member of another VLAN, a routing device or a Layer 3 switch is
required.
There are a number of advantages to VLANs:
❑ Improve network performance
— Grouping end nodes with
related functions in the same virtual LAN can reduce the amount
of data traffic on each segment.
❑ Improve network security
— When networking devices, such as
workstations and servers, are grouped into a VLAN, data is
exchanged only between those members of the group. This can
help to limit unauthorized access to restricted data and network
devices.
❑ Simplify network management
— Moving network devices
between LAN segments can be accomplished through software
management, without having to move the devices physically or
having to rewire connections to switches in the wiring closet.