ECMP: Consistent load balancing for ECMP groups in conjunction with improved failover

Junos OS supports a new functionality to prevent the reordering of flows to already active paths in an equal-cost multipath routing (ECMP) group if one or more path next-hops go down. Before this feature, when a server in the ECMP path failed, the flows directed to that server were redistributed to other, active links. If a second server in the ECMP path also went down, the newly redistributed traffic would be redistributed again, even though the ECMP path is active. The improved failover and traffic rebalancing introduced in this release minimize the traffic redistribution when multiple servers in the ECMP path fail.