One of the most important features of IGRP is its capability to perform multipath routing. Unlike RIP, which only remembers a single route to any given destination, IGRP can remember up to four different routes to any given destination! This allows IGRP to balance traffic loads across multiple routes, while protecting against the impacts of link failures.
Redundant routes may be of equal or different costs. Therefore, IGRP can support two types of load balancing:
Equal-cost load balancing
Unequal-cost load balancing
Equal-cost load balancing, as its name implies, is the balancing of a traffic load across redundant links of equal cost. Figure 10-3 illustrates this in a small network, and the contents ...