1. Introduction-10
1.2.6 VLAN
A virtual LAN (VLAN) is a network of computers that behave as
if they are connected to the same wire, even though they may
actually be physically located on different segments of a LAN.
VLANs are analogous to a group of end stations, perhaps on
multiple physical LAN segments that are not constrained by their
physical location and can communicate as if they were on a
common LAN.
VLANs are configured through software rather than hardware,
which makes them extremely flexible. One of the biggest
advantages of VLANs is that when a computer is physically
moved to another location, it can stay on the same VLAN
without any hardware reconfiguration.
Because VLANs are not limited by the hardware constraints that
physically connect traditional LAN segments to a network, they
can define a network into various logical configurations. For
example, VLANs can define a network by application. In this
scenario, a company might create one VLAN for multimedia
users and another for email users. VLANs can also define a
network by department. For example, a company might have
one VLAN for its Engineering Department, another for its
Marketing Department, and another for its Account Payable
Department.
VLANs can also be set up according to the organization
structure within a company. For example, the company president
might have his/her own VLAN, the executive staff might have a
different VLAN, and the remaining employees might have yet a
different VLAN.
As these examples show, VLANs offer unparalleled flexibility.
