Strict weighted load-balancing is enabled by configuring weighted-ecmp strict in global routing mode. The strict enforcement for a load balancing weight is valid for both a BASE router instance and for a VPRN instance.
With strict enforcement, a weight must be configured on each interface within a wECMP interface bundle before the interface is taken into wECMP operation.
Without weighted-ecmp strict enforcement enabled, and if one or more interfaces within a wECMP interface bundle does not have a load-balancing-weight weight configured, then the wECMP load-balancing falls back to classic ECMP operation and equally spray data-plane traffic across the available interfaces.
A special case of weighted-ecmp strict is when none of the available paths or next-hops have a load-balancing-weight weight value associated. Then, the load-balancing falls back to the classic ECMP.
weighted-ecmp strict is enabled in the router global context for ISIS, OSPF and OSPFv3. Other routing technologies follow classic weighted-ecmp operation.