Chapter 16. Vlan Introduction; Introduction - Allied Telesis SwitchBlade x908 Series Software Reference Manual

VLAN Introduction

Introduction

A Virtual LAN (VLAN) is a logical, software-defined subnetwork. It allows similar devices on the
network to be grouped together into one broadcast domain, irrespective of their physical
position in the network. Multiple VLANs can be used to group workstations, servers, and other
network equipment connected to the switch, according to similar data and security
requirements.
Decoupling logical broadcast domains from the physical wiring topology offers several
advantages, including the ability to:
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Devices that are members of the same VLAN only exchange data with each other through the
switch's layer 2 switching capabilities. To exchange data between devices that are located in
different VLANs, the switch's layer 3 (routing) capabilities are used. The switch passes VLAN
status information to the Internet Protocol (IP) module that indicates whether a VLAN is up or
down. This information is used to determine route availability.
The device supports up to 4094 VLANs (the maximum allowed by the VID field in the 802.1Q
tag). On some devices a few of these VLANs may be reserved for management purposes.
When the switch is first powered up (and therefore unconfigured), it creates a default VLAN
with a VID of 1 and an interface name of vlan1. In this initial condition, the switch attaches all its
ports to this default VLAN. The default VLAN cannot be deleted, and ports can only be
removed from it if they also belong to at least one other VLAN. If all the devices on the
physical LAN belong to the same logical LAN, that is, the same broadcast domain, then the
default settings will be acceptable, and no additional VLAN configuration is required.
16.2
Move devices and people with minimal, or no, reconfiguration
Change a device's broadcast domain and access to resources without physically moving
the device, by software reconfiguration or by moving its cable from one switch port to
another
Isolate parts of the network from other parts, by placing them in different VLANs
Share servers and other network resources without losing data isolation or security
Direct broadcast traffic to only those devices which need to receive it, to reduce traffic
across the network
Connect 802.1Q-compatible switches together through one port on each switch
Software Reference for SwitchBlade® x908, x900 and x600 Series Switches
TM
AlliedWare Plus Operating System - Software Version 5.3.1 C613-50007-01 REV B