Technical data

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VLAN
VLAN or Virtual LAN is a technique that permits grouping of equipment in a common
network. There are several options, on a port level or on a MAC-address level.
Furthermore, there are supplier specific solutions. Historically companies and organisa-
tions have used routers to segment large networks. This segmentation can
also be done using VLAN.
A network with installed equipment forms a common “broad-
cast” domain for all connected devices. If the network needs to be
expanded some form of segmentation is usually necessary, partly
because of speed but also to provide administrative benefits. This is
normally done using one or more routers.
In a network each connection is a separate collision domain,
whereas all equipment belongs to the same broadcast domain, and
because of this all broadcasts will be forwarded to all devices. When
the network is expanded, there is a risk of further broadcasts due to
the connection of more equipment, which in turn limits network per-
formance. Some equipment can also utilise multicast and communicate
data to a number of recipients. All this traffic may need to be limited, which can be
done with routers or with VLAN (Virtual LAN).
The principle is, using a switch with VLAN-support, to specify those devices that are
to be associated to a common virtual network. This virtual
network creates a separate broadcast domain, which elimi-
nates unwanted traffic to the remaining devices. In the
example opposite, B1,B2 and B3 communicate with
each other in a virtual network. The video camera
A1 sends information constantly, but only to A2.
Other devices communicate according to the
standard for a switched network.
Switched
Network
A1
A2
B1
B2
B3
Switched
Network
Net A
Net B
B A C K