About VLANs
89
About VLANs
A VLAN is a group of location-independent and
topology-independent devices that communicate as if
they were on the same physical LAN. Network devices on
different LAN segments and of different media types can
be members of the same VLAN. Membership in a VLAN
is determined by a VLAN tag that is transmitted with the
Ethernet frame for use by a switch.
With VLANs, you can define a network according to:
■
Organizational groups — For example, you can have
one VLAN for the Marketing department and one for
the Finance department.
■
Application groups — For example, you can have one
VLAN for e-mail users and one for multimedia users.
Implementing VLANs on a network has these advantages:
■
It eases the change and movement of devices on
IP networks.
With traditional IP networks, if users move to a different
IP subnet, the IP addresses of each workstation must be
updated manually. With VLANs installed, if an end station
on VLAN 1 is moved to a port elsewhere on the network,
you need only to specify that the new port is on VLAN 1.
■
It helps to control traffic.
With traditional networks, congestion can be caused by
broadcast traffic that is directed to all network devices
whether they require it or not. Each VLAN can be set up
to contain only those devices that need to communicate
with each other, increasing network efficiency.
■
It provides extra security.
Devices within each VLAN can communicate only
with member devices in the same VLAN. If a device in
VLAN 1 needs to communicate with devices in VLAN 2,
the traffic must cross a router.
The Dynamic
Access
software for servers multiple VLAN
capability supports IEEE 802.1Q VLAN tagging and
works with any switch that complies with IEEE 802.1Q
specifications. See your Ethernet switch documentation
for more information on IEEE 802.1Q VLANs.
Book Page 89 Monday, June 7, 1999 2:14 PM
