Load balancing is classified as equal-cost multiple path (ECMP) or unequal-cost multiple path (UCMP). ECMP is automatically implemented by routing protocols, with no need for manual configuration, whereas UCMP is implemented using commands.
ECMP evenly load-balances traffic over multiple equal-cost paths to a destination, irrespective of bandwidth. Equal-cost paths have the same cost to the destination.
UCMP load-balances traffic over multiple equal-cost paths to a destination based on bandwidth ratios. All paths carry traffic based on their bandwidth ratios.