An Introduction to VLAN
One of the first facts about VLAN you should know is its meaning. It stands for virtual local
area network. These are grouped hosts with similar requirement sets that interact as if they are
connected to one domain. This is true irrelevant of its location. The network allows end
stations to be clustered together even if they are in
different network switches.
Setting up an Internet only Network on the Router
Console cable (not needed if Web or telnet setup is possible)
Computer that can link to a router
Router with ISL VLAN encapsulation or IEEE 802.1Q support
The network needs to have a couple of non-overlapping IP address spaces. 192.168.y.x is the
most widely used private address. X is the number for an individual host. Y is any static
number between one and 254. The subnet mask is 255.255.255.0.
Link to the router. This can take different forms. It may be a connection from the computer
serial port to the router’s console port. It can also be a telnet session to the administrative
protocol address. Others may employ a Web interface.
The next step is to set up the virtual sub-interfaces. This is on
the port linking from the switch to the router. The set up will vary depending on the router.
The DOT1Q should be activated for the sub-interfaces. This will provide a unique VLAN ID
number for each. For a Cisco router, the command has to be set separately for every sub-
Another of the facts about VLAN you should know is the sub-interface has to be given a
gateway address. This is the last or first host number of the network. In 192.168.2.x, the
interface would be 192.168.2.254 or 192.168.2.1.
The table for each network has to be configured. The virtual local area network must have the
default route (0.0.0.0) mode directed to the router port linked to the Web. If you are using a
the command is "ip route 0.0.0.0 0.0.0.0 [interface or IP address of next 'hop'].
An access control list has to be set up next. This will prevent anyone on the network from
getting to other networks. Once set up, this can be applied to the Internet-only sub-interface.
In most routers, you have to enter the interface configuration and type a specific command.
Virtual local area networks have different addresses and numbers. To avoid confusion, make
the network name and ID the same. If you are using a Cisco router, descriptions can be added
to the commands.
As these facts about VLAN show, setting it up requires skill and experience. Although the
process is complex, it certainly has its benefits.