User`s guide

DIGITAL MultiSwitch 700 Port Based VLAN User’s Guide 1-1
CHAPTER 1
VIRTUAL LOCAL AREA NETWORKS
This chapter introduces the concepts of Virtual Local Area Networks
(VLANs) and discusses the central concepts of prestandard IEEE 802.1Q
VLANs.
1.1 DEFINING VLANS
A Virtual Local Area Network is a group of devices that function as a
single Local Area Network segment (broadcast domain). The devices that
make up a particular VLAN may be widely separated, both by geography
and location in the network.
The creation of VLANs allows users located in separate areas or
connected to separate ports to belong to a single VLAN group. Users that
are assigned to such a group will send and receive broadcast and multicast
traffic as though they were all connected to a single network segment.
VLAN aware switches isolate broadcast and multicast traffic received
from VLAN groups, keeping broadcasts from stations in a VLAN
confined to that VLAN.
When stations are assigned to a VLAN, the performance of their network
connection is not changed. Stations connected to switched ports do not
sacrifice the performance of the dedicated switched link to participate in
the VLAN. As a VLAN is not a physical location, but a membership, the
network switches determine VLAN membership by associating a VLAN
with a particular port.
Figure 1-1shows a simple example of a port based VLAN. Two buildings
house the Sales and Finance departments of a single company, and each
building has its own internal network. The stations in each building
connect to a MultiSwitch 700 in the basement. The two switches are
connected to one another with a high speed link.