If you ever wanted to set up a network manually, you will quickly find how much overhead is required to get PCs, printers, and other network equipment. That’s where dynamic routing protocols come into play although they are helpful I strongly urge you to understand static routing first. (See the post Configure Static Routing) So for today’s post let’s get the foundation of understanding dynamic routing protocols.
By definition a routing protocol is a set of messages, rules and algorithms used by routers for the overall purpose of learning routes to other networks not physically connected to it. (RIP, EIGRP, OSPF, and BGP are all examples of routing protocols! When using a dynamic routing protocol routers learn “dynamically” about other remote networks and automatically add these networks to its routing table. However keep in mind that when compared to static routing, dynamic routing require less administrator overhead but they will use the routers resources like, more RAM, more processing time (CPU), and even the network bandwidthAlthough there are several routing protocols each of them have their benefits but they all focus on these key things:
- Learn about networks from other neighboring routers and maintain up-to-date routing information.
- Advertise routing information to neighboring routers and thus discovering remote networks.
- If more than route is possible the router will pick the best route based on its metric.
- If the any one part of the network fails, react by advertising the bad routes and advertise the best available route. (Convergence)
Before we go any further about dynamic routing protocols remember there are two type of routing protocols used today:
- IGP (Interior Gateway Protocols) A routing protocol that is designed for a single autonomous system. Some common routing protocols classified under IGP are RIP, IGRP, EIGRP, OSPF, IS-IS.
- EGP (Exterior Gateway Protocols) A routing protocol that is designed for use in between autonomous systems. A common routing protocol classified under EGP is BGP.
Interior Gateway Protocols are used within a company or organization, once that information leaves the company or organization it moves towards the ISP which would use an Exterior Gateway Protocol EGP. So for the picture above think of the clouds to be the inside of a company or organization and outside of that company or organization the routing protocol would change.
For now let’s stop there because the dynamic routing protocols open another door, like Distance Vector and Link-state routing protocols, and the difference between classful and classless routing protocols along with the different type of administrative distances and metrics, these discussions for another day. :) Like always I hope this information was informative and if you have a topic that deals with either ICND1 or ICND2 material let me know by commenting below.
- Configure Static Routing (ciscoskills.net)