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Which Routing Protocol Should My Network Use?

Chapter Description

One of the toughest questions facing network engineers is which routing protocol to use. Each has its strengths, and each works better with some network designs than with others. This chapter will help you decide which routing protocol is best for your particular network.

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What Are the Tradeoffs?

In many networks, the final decision of which routing protocol is "best" comes down to these issues:

  • Convergence speed—How important is convergence speed? How much flexibility do you have in the design of your network around convergence speeds?
  • Predominant topologies—Does your network design have one dominant type of topology? Would a full mesh or large-scale hub-and-spoke topology benefit from running one protocol over another?
  • Scaling strategy—Does your scaling strategy call for dividing the network into multiple pieces, or does it call for a single IGP domain, with the network broken up into pieces through route aggregation and other techniques?
  • Maintenance and management—Which routing protocol fits the network management style of your day-to-day operations? Which one seems easier to troubleshoot and manage in your environment?

Beyond the technical factors are some nontechnical ones. For instance, if you decide to switch protocols, what is the cost for the long term? You need to consider training costs, the cost of revised procedures, design effort, and possible downtime while you convert the network from one protocol to another.

In some situations, this might not be an issue. For instance, if two networks are being merged because of a corporate merger, and each runs a different protocol, the decision might be more open to consideration. If you are going to need to convert one half of the network or the other, you can more carefully consider the technical considerations and make a decision based on those considerations alone. However, if your network is stable today, you should think twice about switching protocols unless a change in the business environment or some major shift in the way the network is built indicates it is an important move to make to meet the needs of the enterprise.