Each routing protocol has their own algorithm as you may have noticed during your CCNA exam studies. The best way to test out these different algorithms is to create your own CCNA lab scenarios or any other CCNA labs that you can think of. The routing algorithm defines the mechanism for sending and receiving routing information. It also defines the mechanism for calculating the best path and adding routes in the routing table. Last but not least, it defines the mechanism for detecting to topology changes.
The two main routing algorithms or better known as routing protocols that you should learn, distance vector and link-state. While both protocols serve similar functions, they’re very different from each other which will be explained briefly in the below.
There are some characteristics of distance vector routing protocols that you should be aware of. For one thing is convergence time when running the less advanced routing protocols such as RIP.Convergence defines how quickly the routers in the network topology share and learn routing information about them selves and their neighbors. The faster the convergence time the more efficient a network due to less down time during convergence changes. The second is that the algorithm is based on the amount of links or hops the packet must take before reaching a destination. The maximum number of hops a route is allowed to take is 15 which is very limited but it should be noted that in most cases a route is usually less than 5 hops.
The scalability of distance vector protocols defines how large network can become before the distance vector protocol can’t handle the sheer size of the particular network. Another important factor is the resources needed to run the distance vector protocol on a network. This includes the requirements such as, memory space, CPU utilization etc. Since distance vector doesn’t require an advanced algorithm the requirement for more powerful hardware to support the routing protocol operation in addition to the packet forwarding process isn’t too taxing. You may have noticed that distant vector doesn’t require too many processing resources which is perfect for smaller networks.
One great advantage for distance vector protocols is that it’s very easy to maintain and control. With just a few commands you can have a fully operational dynamic routing protocol network! This means that there is less overhead but this comes at a price. The price being that there is very limited control over how the protocol operates compared to link-state protocols. This is where link-state truly shines as you can control a lot of different aspects such as which networks should be summarized and which router interfaces shouldn’t participate in routing that particular routing protocol.
Link-state protocol is built to send packets to the most reliable and through the quickest route possible to a destination just link distance-vector. This is about where the similarities end though, as the link-state algorithm and be very complex. Unlike distance-vector, link-state is a very scalable protocol that can handle medium to large sized internet works without to many issues usually. With that said, careful planning must be done as link-state requires a lot of resources from the router and network itself. If you aren’t careful you won’t get the best use out of the protocol and even worse you could potentially bring the network to a halt if you aren’t careful!