Routing Protocols

💡 Introduction

We've covered the basics of how routing works and how routing tables are constructed. Now, let's delve into the magic of how routing tables are kept up-to-date with the quickest paths to destination networks. The protocols we'll be learning about in this video will help you identify routing problems on any network you might support.

🗣️ How Routers Communicate: Routing Protocols

To learn about the world around them, routers use special protocols called routing protocols to share information with each other. This allows a router on one side of the planet to learn about the best path to a network on the other side.

🏛️ Interior vs. Exterior Gateway Protocols

Routing protocols fall into two main categories:

• Interior Gateway Protocols (IGPs): Used by routers to share information within a single autonomous system (AS). An AS is a collection of networks under the control of a single network operator, such as a large corporation or an internet service provider.

• Exterior Gateway Protocols (EGPs): Used for the exchange of information between independent ASs.

🧭 Interior Gateway Protocols: Link State vs. Distance Vector

IGPs are further divided into two categories:

• Link State Routing Protocols: Routers advertise the state of each of their interfaces (links), allowing every router on the AS to know every detail about every other router. Routers then use this information to run algorithms and determine the best path to any destination network.

• Distance Vector Routing Protocols: An older standard where routers simply share their routing tables with neighboring routers. This provides limited information about the overall network state.

📏 Distance Vector Protocols: A Closer Look

Let's explore how distance vector protocols work with an example:

• Router A: Has a routing table entry for network X (10.1.1.0/24) with a path through interface 2 (connected to Router C) and a distance of 4 hops.

• Router B: Is only 2 hops away from network X.

Using a distance vector protocol, Router B sends its routing table to Router A. Seeing that network X is only 2 hops away from Router B, Router A updates its routing table to reflect this new information. Now, it forwards traffic to network X through interface 1 (connected to Router B) instead of Router C.

🧠 Link State Protocols: A More Sophisticated Approach

Link state protocols offer a more sophisticated approach:

• Routers advertise the state of each of their links (interfaces).

• This information is propagated to every other router on the AS.

• Each router uses this information to run algorithms and determine the best path to any destination network.

Link state protocols require more memory and processing power than distance vector protocols. However, they provide a more accurate and up-to-date view of the network, allowing for faster reaction times to changes.

🕰️ The Evolution of Routing Protocols

As computer hardware has become more powerful and cheaper, link state protocols have mostly made distance vector protocols outdated.

💡 Conclusion

Routing protocols play a crucial role in keeping routing tables updated with the best paths to destination networks. Understanding these protocols is essential for troubleshooting routing problems and ensuring efficient data flow across networks.