What is a Local Area Network (LAN)?
Quick definition: A Local Area Network (LAN) is a network of interconnected computers, devices, and resources within a limited area, such as a home, office, or campus. LANs facilitate communication and resource sharing among connected devices like printers, computers, and scanners.
Nearly all aspects of networking are part of a LAN (Local Area Network) or used to support a LAN. LANs are a fundamental building block of network architecture, and are used by every organization on the globe. They are often connected with Ethernet, WiFi, or fiber optics, and require hardware devices such as routers, firewalls, switches, and gateways. As ubiquitous as they are, it still may not be clear exactly what a LAN is.
Throughout this article, we’ll discuss the ins and outs of LANs, their benefits, and how to set one up. That way, you’ll be ready to tackle the Network+ Exam, or even establish your own LAN.
What is a Local Area Network?
A LAN is a grouping of computers, printers, and other devices that share common resources within a limited geographical area. LANs help businesses and individuals share files, data, and other digital resources in a fast and reliable fashion.
For example, an office branch at a paper company could have one printer. Each computer is connected to the printer so employees can print documents. This grouping of computers and printers would constitute a LAN. However, things quickly get more complex as more employees join the branch.
More nodes mean additional hardware devices, such as routers and switches, to route traffic efficiently. Next, the paper company will need to access the internet to research their next sales. That means they need an internet gateway. Then, to ensure no one tries to hack them from the internet, they require a firewall. As you can see, each piece of LAN hardware is specifically needed to meet the concerns of an ever-growing organization.
Now that we have a good understanding of a LAN's purpose, how does it actually work? Let’s get into that.
How Does a Local Area Network Work?
We've already discovered that LANs can be simple (one printer and a couple of computers) or vast networks that include hundreds of devices and multiple functions. LANs work by using nodes, TCP/IP, routers, and switches. Here's how all those different pieces work together.
Local Area Network Nodes
The most important part of a LAN is the actual nodes on the network. A node is anything that has a NIC (Network Interface Card) in it. That is, anything that can send and receive data via the TCP/IP internet protocol. A node can be a computer, printer, scanner, smartphone, or any device that can communicate with other devices.
TCP/IP
TCP/IP (Transmission Control Protocol/Internet Protocol) delivers data via the LAN and, subsequently, the internet. All LANs send data to and from nodes using TCP/IP, and the data are known as packets. TCP is a fundamental building block of LANs and the internet as we know it.
Local Area Network Routers
If nodes are the destination, and TCP packets are the traffic, then naturally, there must be a traffic director somewhere. That traffic director comes in the form of a router. A router is a critical component on a LAN that ensures packets are properly routed to their intended destination. Generally, they are used to provide access to the internet, or a WAN.
Routers are Layer 3 devices that route traffic using their IP (Internet Protocol) addresses. An IP address is a 4-octet number that represents the address of a node. You have probably seen it before; here is an example: 192.82.12.22. Routers are complex devices and also serve as gateways to the wider internet, sometimes though that is a little overkill. There are many instances when you just want to route traffic between several internal devices; that’s where Switches come in.
Local Area Network Switches
Switches are Layer 2 hardware devices that use the MAC (Media Access Control) address on the device’s NIC to forward traffic. While routers intelligently route traffic to and from the LAN, a switch simply forwards and filters packets to their desired destination. Ultimately, when you imagine the backbone of a LAN, think router. When thinking about connecting internal devices, thing switches.
Routers, nodes, TCP, and switches are just a few devices needed to establish an enterprise LAN. While it may seem like a lot of work, it is well worth it. Let’s find out why.
What are the Benefits of Using a Local Area Network?
The benefits of having a LAN in your organization are so abundant, it would be hard to list them all. If your organization didn't have a LAN, then your office would look like it came straight out of Mad Men. LAN— and IT in general—are a defining characteristic of our contemporary office building. Let’s walk through why that is, starting with the most obvious: resource sharing.
LAN Resource Sharing
Imagine a world where LANs did not exist, and every employee had their own personal printer next to their computer desk. The organization’s IT budget would skyrocket, and would quickly be untenable. That is what the world would be like without LAN resource sharing.
Thanks to LANs, all employees can share printers. Each computer will be connected to a switch via Ethernet cables, and then that hub will connect to the printer. This provides huge savings to the organization, and convenience for the worker.
LANs also allow for the sharing of digital resources. When all the computers are interconnected, files, videos, and emails can easily be stored and shared in a NAS (Network Attached Storage).
Command and Control
The most important responsibility of an organization is providing a secure work area for both their customers and employees. LANs provide the capability to monitor all traffic that enters and leaves the organization's IT network. Firewalls and ACLs enable LANs to block or allow certain ports, protocols, and IP addresses from entering the LAN from the internet. This mitigates the threat of digital theft, malware, and ransomware.
Not only that, but CCTV and other physical security devices can be connected to a LAN. Providing a central location for threats facilitates immediate responses to neutralize any threat to the employees.
Internet Access for Local Area Network
Most organizations would struggle without access to the internet. LANs provide a method for each employee to access the internet from their workstation. Every LAN is connected to a router, which, in turn, is connected to the internet (unless there is a specific reason you want to keep your LAN internet-free).
From the internet’s point of view, the LAN is a subnetwork of machines it can interact with. That means the internet recognizes one IP address associated with the router, but the IP addresses within the network are not recognized by the internet itself, only internally. This is called a subnetwork.
Client-Server Architecture
Client-server architecture allows apps and software to be shared among users. This architecture dramatically enhances the management and accessibility of applications. Suppose the system administrator needs to apply patches or restrict access to applications. In that case, it can be done in one place instead of going to every machine and performing the operation.
How to Set Up a Local Area Network (LAN)
Setting up a LAN is fairly straightforward, but becomes more complex as more machines are added. However, even as it increases in complexity, the steps are fundamentally the same. Let’s begin by listing the bare necessities required to DIY a LAN.
Router
Routers are critical to accessing the internet and managing traffic. Make sure your router has enough ports to accommodate the amount of machines on your LAN.
Switches
If you plan to connect multiple devices to the LAN, it might be beneficial to use switches. These devices will increase the number of available ports and organize your LAN in a more structured manner.
Ethernet Cables
You’ll need hundreds of feet of Ethernet cable. These cables connect nodes to each other and provide connectivity. Cat5, Cat6, and Cat7 cables will all work great.
Computers/Devices
Computers, scanners, fax machines…all of these are integral to making sure your LAN functions properly. The key thing to remember is that each device needs to have an NIC card so that it will have an IP address to route to.
Modem
Lastly, you’ll need a modem (Modulator/Demodulator). Often, these are combined with the router, and we call those gateways. However, if you do not have a gateway, a separate purchase of a modem is required.
Configuring a Local Area Network
Now that we know what hardware is required, it’s time to figure out how exactly all these pieces come together. Here is a high-level overview of how to set up a LAN in four steps.
Step 1: Connect the Devices
Take all of the devices and connect them together. Each device ultimately needs to be connected to the router. This often means running cable through walls, under floors, and down hallways. Ensure you have a comprehensive wiring plan before connecting all the devices. Also, make sure the router is plugged in and turned on.
Step 2: Access Router Setting
Here comes the high-tech part. Connect to your router via Ethernet cable and log in. This can be done by navigating to the router’s default IP address, which will be labeled in the instructions. Additionally, all login credentials will come with the router’s manual.
Step 3: Configure LAN Settings
Next, enable DHCP on the router. This will automatically assign IP addresses to all the devices on your LAN. If you have WiFi, this is where you'll configure that as well. This will be done by configuring the SSID in the router.
Step 4: Connectivity
Test the internet connection by connecting a computer to the router. Then, connect multiple computers to the LAN and verify you can access the share drives. Lastly, make sure internet access is available.
And there you have it, a high-level overview to configure a LAN. Seems simple, but the devil is in the details. Let’s go over some common troubleshooting steps.
How to Troubleshoot Common Local Area Network Issues
Once a LAN is established, it is fairly resilient to critical issues. However, common problems such as latency and connectivity can arise. Let’s go over a couple troubleshooting methods, starting with the basics and moving on to the more advanced.
Verify Physical Connectivity
With so many cables and wires, it is easy to overlook physical connectivity. Verify all hardware is plugged in and connected.
Restart Devices
Often, devices need to be restarted to regain connectivity. Power cycle each device one at a time. If the problems persist, power cycle the next device in the chain of communication.
Check the Firewall and ACLs
Firewalls will often be the culprit for connectivity issues. Verify that the ports required are open and that the IP addresses can transmit data. Next, verify the ACLs (access control lists) on your router are not unintentionally blocking traffic once it enters the LAN.
Update Network Drivers
Verify all network drivers are up-to-spec. Often, outdated drives will lead to connectivity and latency issues.
These are just a few of the many steps that can be taken to troubleshoot a LAN. The most important thing to remember is to start with the obvious and work your way up.
Final Thoughts on Local Area Network
LANs are a keystone concept in networking and are integral to our everyday lives. LANs are simply a group of interconnected devices that share resources. They are connected via Ethernet cables, which lead to a router. LANs provide client-server architecture, facilitating safe and easy software deployment to a host of machines on the network.
LANs will appear on the Network+ Exam, so it is important to have a firm grasp of how they work and how to troubleshoot them. This LAN primer only scratches the surface of the knowledge needed to become a competent network engineer. Here are a couple more great posts to continue your journey.
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