Crash Course: Interior Routing Protocols

Growing pains can cause network pains. As your network expands, you may need a new routing strategy. Choosing the right interior routing protocol is important to maintain consistency and deliver business applications from end to end without undue costs or delays.

In selecting an interior routing protocol, remember the goals of a routing protocol: eliminate loops in the network; quickly detect, advertise and route around unavailable networks; and minimize routing bandwidth use. But even the right routing protocol can't save a poorly designed network, so don't ignore network design and topology.

Controlling network overhead over slow WAN links is a big concern. The less information sent over the links, the better. However, that may limit the information routers need to make routing decisions, so it's a tricky balance.

Before we go too far, let's make sure we're on the same I/O block. A routing protocol is a set of rules by which a Layer 3 router determines the best path, or least-cost route, for a packet or datagram to take to a remote network or endpoint. The routing protocol also dictates how routers send updates to each other, so each knows about interior and/or exterior networks.