Load balancing for layer-2 link aggregation involves initial assignment of link aggregation keys (LAGKs) and reassignment of LAGKs when a load imbalance condition that merits action is discovered. Load conditions change dynamically and for this reason load balancing tends to also be dynamic. Load balancing is preferably performed when it is necessary. Thus an imbalance condition that triggers load balancing is preferably limited to conditions such as when there is frame drop, loss of synchronization or physical link capacity exceeded.