Which routing protocol is capable of performing unequal-cost load-balancing?

The ability to perform unequal-cost load-balancing is a distinctive feature of EIGRP (Enhanced Interior Gateway Routing Protocol). EIGRP can balance traffic over multiple routes to a destination that have different metric values, allowing for more efficient use of available bandwidth. By default, EIGRP uses a ratio known as the "variance" to determine how much more traffic can be sent over a route with a higher metric when compared to the best path.

In contrast, other protocols like RIP, OSPF, and IS-IS typically support equal-cost load balancing only. This means these protocols will distribute traffic evenly across paths that have the same cost metric, but they do not utilize routes that have higher costs, regardless of whether those paths are less optimal. Therefore, EIGRP’s capability for unequal-cost load-balancing sets it apart, allowing for improved resource utilization and performance in networks with diverse path metrics.