What is Routing? Introduction to Routing and the Role of Routers

Have you ever wondered how your emails or YouTube videos reach your computer in the blink of an eye? It’s all thanks to technologies like routing and routers. These terms might seem a bit technical, but don’t worry: in this article, we’ll demystify them together. We’ll see how networks work, why routers are essential, and how routes allow your data to travel from point A to point B.

What is Routing?

Routing is simply the process that determines the path data must take on a network to reach its destination. Imagine you’re sending a letter. You need to know which address to write, where the letter should pass (through the local post office, then maybe a sorting center, etc.), and finally, it arrives at the recipient. Well, for data traveling on the Internet, it’s somewhat similar!

The information you send (like an email or a request to access a web page) is broken down into small data packets. These packets must then find the fastest and most efficient path to reach their destination. This is where routers and routes come into play.

The Role of Routers

A router is a device that sits on the path between your device (computer, smartphone, etc.) and the rest of the network. Its main job is to read the destination address of each data packet and then decide which path these packets should take to reach their goal. In short, it’s like a GPS for data.

How Does a Router Work?

1. Reading the Destination Address: Every device connected to the Internet has a unique address called an IP address (like a house number on a street). The router looks at this address to know where the data should go.
2. Finding the Most Efficient Route: The router has a sort of map (called a routing table) that shows the different possible paths for each destination. It then chooses the best path based on criteria like distance, network traffic, and speed.
3. Sending the Data: Once the route is chosen, the router sends the data to its next step. This process repeats from one router to another until the data reaches its final destination.

What is a Route?

A route is simply a path that data follows to go from one point to another. In the digital world, there are several possible routes, just like there are several roads to go from one city to another.

Types of Routes

1. Static Routes: These are manually defined by a network administrator. It’s like manually programming your GPS to always take the same streets, no matter what.
2. Dynamic Routes: These are automatically determined by the router using routing protocols. These protocols allow routers to “talk” to each other to exchange information and find the best path in real-time. This allows the path to adapt if, for example, a route is congested or down.

Why is Routing Important?

Imagine a world without routers or routing. Every time you tried to connect to a website, your device would have to find all possible paths to get there by itself. It’s not only inefficient but downright impossible to manage with the billions of devices connected worldwide. Routing allows the Internet to function quickly and efficiently, even with massive traffic.

A Simple Example: The Journey of Your Data

To illustrate all this, let’s take an example: you want to access a web page. Here’s what happens behind the scenes:

1. Requesting Access to the Page: You type the address of a website (like “www.example.com”) and press “Enter”.
2. Sending the Request: Your request is broken down into several small data packets, each with a destination address (the IP address of the website).
3. The Role of the Router: Your home router receives these packets and looks at where they need to go. It then chooses the best route and sends the packets to the next router on their path.
4. Traveling of the Packets: The packets travel from one router to another until they reach the website’s server.
5. Receiving the Data: Once the server receives your request, it sends back data packets (the website content) that take the reverse path to return to you.

Routing Protocols: These Silent Allies

Routers don’t do everything on their own. They use routing protocols to learn the best routes. Here are some common examples:

• RIP (Routing Information Protocol): A simple protocol that allows routers to share information about routes. Each router sends its “view” of the routes to others. It’s effective in small networks.
• OSPF (Open Shortest Path First): A more advanced protocol that always finds the shortest and fastest path. It’s used in large networks.
• BGP (Border Gateway Protocol): The protocol used to guide traffic on the Internet itself, between different access providers (like Swisscom, Salt, Sunrise, etc.).

Routing, though invisible to most users, is one of the essential technologies that allow the Internet to function smoothly and efficiently. Thanks to routers and routes, data always knows where to go, even in the vast network that is the Internet.

But it doesn’t stop there. It’s also important to understand how data flows between different segments of the same network. Let’s now talk about subnet routing and VLAN routing, two key concepts for ensuring communication between different parts of a network.

Subnet Routing

When we talk about subnets, we refer to dividing a network into several smaller segments. The goal of this segmentation is to improve network efficiency, better manage IP addresses, and enhance security.

Why Divide a Network into Subnets?

Imagine a company with a very large network, grouping hundreds or thousands of machines. If all these machines are in the same network (or subnet), it can quickly become unmanageable. You would have a lot of “parasitic” traffic circulating between machines, even if they don’t need to communicate with each other. To solve this problem, we divide the network into smaller subnets, each with its own range of IP addresses.

For example, instead of having a single network with the IP address 192.168.1.0/24 for 256 devices, we can divide it into several subnets: 192.168.1.0/26, 192.168.1.64/26, etc.

How is Subnet Routing Done?

In a network divided into subnets, a router is essential to allow communication between these different segments. Each subnet has a default gateway (usually the router’s IP address for that subnet), and it’s this router that will route traffic from one subnet to another.

Let’s take a concrete example:

• Subnet A uses the address range 192.168.1.0/24.
• Subnet B uses the address range 192.168.2.0/24.

If a device in subnet A (say IP address 192.168.1.10) wants to communicate with a device in subnet B (for example, 192.168.2.15), here’s what happens:

1. Sending the Data: The device in subnet A sends its packets to the gateway of its subnet (the router) because it doesn’t directly find the destination device in its own subnet.
2. Routing: The router receives the packets, consults its routing table to see where it should send the data, and transmits it to subnet B.
3. Receiving the Data: The packets reach their destination in subnet B.

The Importance of the Subnet Mask

A crucial element of subnet routing is the subnet mask. The mask allows dividing IP addresses into two parts: the network identifier and the host identifier. This allows the router to know which addresses belong to which subnet and to direct traffic accordingly.

VLAN Routing (Inter-VLAN Routing)

VLANs (Virtual Local Area Networks) are another way to segment a network, but this time virtually, within the same physical network. This allows logically separating devices on the network, even if they are connected to the same hardware.

What is a VLAN?

A VLAN is a virtual local network that allows grouping devices connected physically to different switches as if they were in the same network. Conversely, the same switch can also host multiple VLANs, thus logically separating the data flows of the devices connected to that switch.

For example, in a company, you can have a VLAN for the HR department, another for accounting, and another for the IT department. Even if all devices are plugged into the same physical switches, VLANs will logically isolate them, preventing them from directly communicating with each other.

The Role of Inter-VLAN Routing

Even though VLANs allow segmenting the network, there are often times when devices in different VLANs need to communicate with each other. This is where inter-VLAN routing comes in.

Inter-VLAN routing is done via a router or a Layer 3 switch (also called a multilayer switch). A Layer 3 switch combines the functions of a traditional switch (Layer 2) and a router. It allows routing traffic between VLANs while ensuring local communication within each VLAN.

How Does Inter-VLAN Routing Work?

1. Creating VLANs: Each VLAN is configured with a unique IP address range and a VLAN identifier (a number, often between 1 and 4094).
2. Assigning Switch Ports to VLANs: The physical ports of the switch are assigned to different VLANs, allowing logically grouping the devices connected to those ports.
3. Routing Packets Between VLANs: When a device in one VLAN (say VLAN 10) wants to communicate with a device in another VLAN (say VLAN 20), the data must pass through a router or a multilayer switch. The latter uses its routing capabilities to transfer packets from one VLAN to another.

Differences Between Subnet Routing and VLAN Routing

Although similar in concept (making network segments communicate with each other), there are important differences between subnet routing and VLAN routing:

• Physical vs. Virtual: Subnets are often physical divisions of a network (different cable segments, different gateways), while VLANs are virtual divisions on the same physical network.
• Infrastructure: Subnet routing is generally done with a standard router, while VLAN routing requires a router or a Layer 3 switch capable of handling VLANs.
• Data Isolation: VLANs offer stricter isolation because even if two devices are physically connected to the same switch, they cannot directly communicate if they are not in the same VLAN. Subnets can be more permissive if poorly configured.

Why Use VLANs?

VLANs are particularly useful for security and network management. For example, in a company, you might want sensitive departments, like finance or HR, to be completely isolated from other parts of the network. You can also use VLANs to assign different priorities to certain data flows, like for VoIP (Voice over IP), to ensure good quality of service.

Conclusion

Whether you’re exploring the basics of routing to understand how data travels across the Internet or looking to master more advanced concepts like subnet routing and VLAN routing, routing remains at the heart of the proper functioning of networks. In an increasingly connected world, these mechanisms not only allow efficient communication but also optimized and secure management of infrastructures, whether personal or professional.

Subnet routing helps you divide a network to better manage and structure traffic, while inter-VLAN routing ensures strict isolation and increased flexibility to organize data flows within the same physical network. Whether configuring a home network or managing a complex corporate environment, these concepts will be essential pillars for creating robust and high-performing networks.

So next time you’re configuring a router or thinking about your network’s organization, remember these principles. With a good understanding of routing, you’ll have the keys to building reliable, secure infrastructures ready to handle any situation.

Enjoy 😎

AlexIn Tech