Benefits of VLANs
Implementing VLANs on your network has three main advantages:
■It eases the change and movement of devices on networks.
■It helps to control broadcast traffic.
■It provides extra security.
How VLANs Ease Change and Movement
With traditional IP networks, network administrators spend much of their time dealing with moves and changes. If users move to a different IP subnet, the IP addresses of each endstation must be updated manu- ally.
With a VLAN setup, if an endstation in VLAN 1 is moved to a port in another part of the network, you only need to specify that the new port is in VLAN 1, and this is something that can be done remotely if you have 3Com’s Transcend Enterprise Manager for Windows (v6.0 and above).
How VLANs Control Broadcast Traffic
With traditional networks, congestion can be caused by broadcast traffic that is directed to all network devices whether they require it or not. VLANs increase the efficiency of your network because each VLAN can be set up to contain only those devices that need to communicate with each other.
How VLANs Provide Extra Security
Devices within each VLAN can only communicate with 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. Routers have filtering and security features to block unauthorized access.
Figure 7-1 shows a network configured with three VLANs—one for each of the departments that access the network. The membership of VLAN 1 is restricted to ports 1, 2, 3, 4 and 5 of Switch A; membership of VLAN 2 is restricted to ports 4, 5, 6, 7 and 8 of Switch B while VLAN 3 spans both Switches containing ports 6, 7, 8 of Switch A and 1, 2, 3 of Switch B.
In this simple example, each of these VLANs can be seen as a ’broadcast
Specific configurations using the Switch are shown later in this chapter.
