Tuesday, 22 December 2015


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It is no news that offices around the world depend on the processing power of computers to successfully run their day to day business. It is also important to know that offices that connect these computers together in whatever form are seen to be more organized and corporate than those that do not. Computer networking, the connection of various computers and devices (e.g. printers, scanners) for the purpose of resource sharing comes in different flavors. The type of networking solution employed depends on the size of the office as well as the operations carried out.
This post is focused on providing networking solutions to medium-sized offices using the concept of virtual local area networks. I’ll start by telling you what LANs and VLANs actually are, after which I’ll discuss how VLANs can be implemented in networking offices.

This tutorial is targeted at individuals with basic knowledge of networking, especially how to cable a network as well as bring up routers and switches and perform basic configurations. If you are also preparing for the Cisco Certified Network Associate (CCNA) this tutorial will be of benefit for you since VLAN configuration is one of the CCNA exam objectives.

To get this tutorial completely dialed in you need to have in your possession the following:

  • ·         Switch
  • ·         Router
  • ·         Straight through cables
  •      At least 3 PCs

You can get used switches and routers on ebay for around 30 dollars each and the prices keep dropping. They’re old ones actually but will be okay for this tutorial. Now I know not everybody can afford them and that is why you should get the cisco packet tracer network simulator if you fall in the this category. Those preparing for CCNA exam should be familiar with it. Other simulators you can use are router sim and GNS3.


Local Area Network (LAN)
This is the connection of computing devices on a local segment for the purpose of sharing files and services (e.g. print services, internet connection etc.). Devices such as hubs and switches are used along with the right cabling to actualize local area networking. Switches are more optimal than hubs as they provide advanced functions like segmentation, MAC address learning and make forward/filter decisions for sending and receiving frames based on the addresses learned.

Virtual LAN
Basically, a virtual LAN is a logical grouping of users by function. With virtual LANs,  network hosts that perform similar tasks are grouped into separate VLANs. To illustrate this further, consider an organization with different departments or sections, say finance, sales and advertising departments. Each of these departments can be put in their VLANs so that data meant for only staffs working in the sales department are not necessarily broadcasted to the rest of the network. Broadcast control is one of the major benefits of using VLANs. VLANs also enhance network security, and increase the number of broadcast domains while decreasing their size. This means that in a network without routers, the OSI layer 3 function of broadcast control can only be achieved at layer 2 by implementing VLANs. 

The use of VLAN in a network is a cost-benefit solution for organizations that do not want to spend much on routers but still desire network flexibility and scalability.

Someone out there may be asking; what if these sections in separate VLANs need to communicate in order to share general information? Shouldn’t there be a way to link them?
The answer to that question is inter-VLAN routing.
Inter-VLAN routing allows for communication between VLANs and to make this happen, we need a router.


We are now going to use the case study of a fictional organization named iDAP with 3 different departments namely; sales, admin, and marketing to illustrate how VLAN can be implement using a switch and a router. The diagram below is the iDAP’s network topology.


The cable connections are done using straight through cables.
The tutorial continues in the second part which is a step by step guide to configuring VLAN in our network using cisco routers and switches or those with cisco inter-network operating system (IOS) installed. Try to get some good Cisco switches and routers to implement this network.

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