Dynamic routing protocols enable routers to automatically discover and share network information, eliminating the need for manual route configuration. This content covers how these protocols function, their evolution over time, and the three core components that define them.
Dynamic Routing Protocols
In a previous module we went over some ways that a router would learn of other networks. One of those is a directly connected network. When we set up a local link on a router, then it becomes aware of that network that it's directly connected to. So for router 1, when we set up this interface, it then learns that that is a network that's connected to it, it's a directly connected network. And then it learns of this network, because once again we set up that interface and then it understands that it's part of that network.
What it doesn't know about is these remote networks, and in this example right here there are many remote networks that it needs to learn. What a dynamic routing protocol does is allow two of these devices to speak together, or actually really all of these devices to speak together, and they will transfer information back and forth. So router 1 then learns of all of the directly connected networks that this layer 3 switch has, it learns of the directly connected network that this router 2 has, which is this network right here, and then it also learns of this distant remote network that's attached to this router 3. All of that information goes into the routing table on R1, and now R1 knows where to direct traffic. So that's what a dynamic routing protocol does: it allows communication to happen between two of these devices.
You don't need to know an in-depth history about these routing protocols, but you do call us out just to drive home the point that there are many different routing protocols, each with their strengths and weaknesses, and they have developed differently over the ages. As an example of this, RIP version one came out in 1988, then RIP version 2 came out in 1994, which had some adjustments as we brought on things like the LSM, and then RIPng came out when we started developing IPv6. So there are different reasons to choose the different routing protocols.
There are three components that make up a dynamic routing protocol. First of all is the data set, then we have the messages, then we have the algorithm that it uses to determine how to interpret the data.
What that looks like is, for RIP let's say, it has a different set of tables, a different set of databases, that go into RIP and how RIP functions, and that's going to be different than the data set and the tables and the databases that something like OSPF or EIGRP would use. Same thing with the messages and how the messages get transferred back and forth between these devices: those messages are going to look quite a bit different depending on what routing protocol you use. And then finally, the algorithm is the set of instructions, the set of rules, the set of processes that the data goes through to determine how it's going to route the information, and there are some drastic differences between how RIP works and how EIGRP works and how OSPF works. So these are the different components that are designed to go into these dynamic routing protocols.
The three components a dynamic routing protocol has are the messages that are sent back and forth, how it transfers the data; how it stores that data in databases and tables; and then finally how it calculates the best path using an algorithm. So those are the three components — the data set, the messages and the algorithm — that these different protocols will use to determine the best path.
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