Vlan Configuration; Introduction To Vlan; Vlan Overview; Vlan Fundamentals - HP A5120 EI Series Configuration Manual

VLAN configuration

Introduction to VLAN

VLAN overview

Ethernet is a network technology based on the Carrier Sense Multiple Access/Collision Detect
(CSMA/CD) mechanism. Because the medium is shared, collisions and excessive broadcasts are
common on Ethernet networks. To address the issue, virtual LAN (VLAN) was introduced to break a LAN
down into separate VLANs. VLANs are isolated from each other at Layer 2. A VLAN is a bridging
domain, and contains all broadcast traffic within it.
Figure 31 A VLAN diagram
Router
A VLAN is logically divided on an organizational basis rather than on a physical basis. For example,
using VLAN, all workstations and servers that a particular workgroup uses can be assigned to the same
VLAN, regardless of their physical locations.
VLAN technology delivers the following benefits:
Confining broadcast traffic within individual VLANs. This reduces bandwidth waste and improves

network performance.
Improving LAN security. By assigning user groups to different VLANs, you can isolate them at Layer

2. To enable communication between VLANs, routers or Layer 3 switches are required.
Creating flexible virtual workgroups. Because users from the same workgroup can be assigned to the

same VLAN regardless of their physical locations, network construction and maintenance are much
easier and more flexible.

VLAN fundamentals

To enable a network device to identify frames of different VLANs, a VLAN tag field is inserted into the
data link layer encapsulation.
VLAN 2
Switch A
VLAN 5
Switch B
101