Configuring Vlans; Overview - HP 6600 Configuration Manual

Configuring VLANs

The VLAN feature is supported on SAP modules that are operating in bridge mode.

Overview

Ethernet is a shared-media network based on the CSMA/CD mechanism. A LAN built by using Ethernet
is both a collision domain and a broadcast domain. In a LAN with plenty of hosts, the LAN might be full
of collisions and broadcasts. As a result, the LAN performance is degraded or even the LAN becomes
unavailable. You can deploy bridges or Layer 2 switches in the LAN to reduce the collisions, but this
cannot confine broadcasts. To address the issue, virtual LAN (VLAN) was introduced to break a LAN
down into separate VLANs. Hosts in the same VLAN can directly communicate, and hosts of different
VLANs cannot directly communicate. For example, hosts in VLAN 2 can communicate with each other,
but cannot communicate with the hosts in VLAN 5. A VLAN is a broadcast domain, and contains all
broadcast traffic within it, as shown in
Figure 29 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
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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.
Figure
VLAN 2
Switch A
VLAN 5
29.
Switch B
88