VLAN

Virtual Local Area Networks, or VLANs, allow a network manager to segment a LAN (Local Access Network) into different domains. The segmentation is a logical setup and not a physical one. It removes the proximity requirement of LANs. VLANs remove the need for routers to define broadcast domains. All you need is a bridging software program to define workstations to be included in the broadcast domain. A router is only needed when communicating with another VLAN.

Setting Up the VLAN

Assignment to a VLAN is done at the switch level. The switch is the backbone of all available VLANs in a network. The switch has two configurations: trunk mode, and normal mode. These modes are designed to deliver maximum functionality to the network.

Decide on the environment. It is up to you if you want your VLAN to span a lot of switches or if you want to segment a single switch. If you have just one switch, this means you can configure other VLANs without other considerations. On the other hand, if you have multiple switches, you will have to decide which VLANs will be assigned under which switch. You will also have to set up the trunking and the VLAN trunking protocol.

Configuring

You will need these codes to properly set up the VLAN.

‘SwitchA# vlan database’

‘SwitchA(vlan)# vlan 2 name vlan2’

‘SwitchA(vlan)# exit’

‘SwitchA# configure terminal’

‘SwitchA(config)# interface fastethernet 0/1’

‘SwitchA(config-if)# switchport mode access’

‘SwitchA(config-if)# switchport access vlan 2’

‘SwitchA(config-if)# end’

Use these commands from a privileged mode to create VLAN Number 2. VLAN Number 1 is already there for the management of VLAN so always number created VLANs from 2-1000.

Trunking must be configured at this point because it will allow VLAN information to pass between switches. Set up the trunk mode and the trunk encapsulation mode so they will match. Otherwise, the manner that frames are identified in the data transfer process may not match your VLAN and therefore will not be effective. Remember to configure the rest of the setup according to the way you want your VLAN to work.

Additional Reading on VLAN