VLAN
Understanding VLANs
Virtual LANs (VLANs) are a feature of most switches
today, where the administrator
groups ports on a switch by placing the ports in a virtual
LAN. When a port is configured
for a particular VLAN, it is unable to communicate
with systems that are not on that
VLAN without the use of a device such as a router.
This is similar to the fact that if we
had two physical networks, a machine could not send
data from one network to the other
without the use of a router.
The purpose of a VLAN is to cut down on broadcast
traffic through the use of what are
known as broadcast domains. Let’s look at how this
works. Normally, if we had a 24-port
hub or switch and a computer wanted to send data to
all systems, it would “broadcast” the
data out onto the network. A broadcast will hit every
port on that switch or hub. With a
VLAN-supported switch, you can create VLANs that act
as “broadcast” domains. This
means that if Workstation A is on VLAN1, which is made
up of ports 1 through 12 on the
24-port switch, when Workstation A sends broadcast
traffic (traffic intended for all
systems), it will be sent only to ports 1 through 12
because the virtual LAN is acting as a
boundary for traffic. The benefit of this is that you
are now able to minimize traffic within
or across switches, which increases network
throughput. Figure 1 shows a switch that
is divided into two different VLANs.
Ports
on a switch associated with VLANs
To create the VLANs, the network administrator will
need to run the configuration
utility on the VLAN-supported switch. Also note that
with a layer-1 switch, if a system
needs to be moved from VLAN1 to VLAN2, there is no
need to move systems around;
you simply need to configure the port that the system
is connected to from one VLAN to
the other on the switch.a
excellent
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