Lack of Load Balancing

Another of RIP's significant limitations is its inability to dynamically load balance. Figure 8-20 illustrates a router with two serial connections to another router in its internetwork. Ideally, the router in this illustration would split the traffic as evenly as possible between the two serial connections. This would keep congestion to a minimum on both links and would optimize performance.

Figure 8-20: A router with redundant serial connections.

Figure 8-20: A router with redundant serial connections.

Unfortunately, RIP cannot perform such dynamic load balancing. It would use whichever of the two physical connections that it knew about first. RIP would forward all its traffic over that connection even though the second connection was available for use. This scenario would change only if the router in Figure 8-20 received a routing update informing it of a change in the metrics to any given destination. If this update meant that the second link was the lowest-cost path to a destination, it would begin using that link and cease using the first link.

RIP's inherent lack of load-balancing capability reinforces its intended use in simple networks. Simple networks, by their very nature, tend to have few (if any) redundant routes. Consequently, load balancing was not perceived as a design requirement, and support for it was not developed.

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