Unequal Metric Route Load Sharing
Convergence to a feasible successor route should happen within a second after a router realizes the successor route has failed. Even in large well-designed networks, particularly with features like stub routers and route summarization in use, convergence can still happen in a reasonable amount of time even when going active. The next feature, load sharing, takes convergence to another level, giving instantaneous convergence, while reaching other goals as well.
Cisco IOS allows routing protocols to place multiple routes into the routing table for an individual prefix/length. Cisco IOS then balances traffic across those routes, by default balancing traffic on a per-destination IP address basis.
Load balancing, ...