Weighted ECMP is supported within an endpoint or a label-binding policy when the NHGs are of resolution type direct. Weighted ECMP is not supported with an NHG of type indirect.
Weighted ECMP is performed on labeled or unlabeled packets forwarded over the set of NHGs in a forwarding policy when all NHG entries have a load-balancing-weight configured. If one or more NHGs have no load-balancing-weight configured, the spraying of packets over the set of NHGs reverts to plain ECMP.
Also, the weighted-ecmp command in GRT (config>router>weighted-ecmp) or in a VPRN instance (config>service>vprn>weighted-ecmp) are not required to enable the weighted ECMP forwarding in an MPLS forwarding policy. These commands are used when forwarding over multiple tunnels or LSPs. Weighted ECMP forwarding over the NHGs of a forwarding policy is strictly governed by the explicit configuration of a weight against each NHG.
The weighted ECMP normalized weight calculated for a NHG index causes the data path to program this index as many times as the normalized weight dictates for the purpose of spraying the packets.