The weighted load-balanced, or weighted-ecmp, feature sprays packets of IGP, BGP, and static route prefixes, resolved to a set of ECMP tunnel next hops, proportionally to the weights configured for each MPLS LSP in the ECMP set.
Weighted load balancing is supported in the following forwarding contexts:
IGP prefix resolved to IGP shortcuts in RTM (igp-shortcut or advertise-tunnel-link enabled in the IGP instance)
BGP prefix with the BGP next hop resolved to IGP shortcuts in RTM
Static route prefix resolved to an indirect next hop, which is resolved to a set of equal-metric MPLS LSPs in TTM. The user can allow automatic selection or specify the names of the equal-metric MPLS LSPs in TTM to be used in the ECMP set.
Static route prefix resolved to an indirect next hop, which is resolved to IGP shortcuts in RTM
BGP prefix with a BGP next hop resolved to a static route, which resolves to a set of tunnel next hops toward an indirect next hop in RTM or TTM
BGP prefix resolving to another BGP prefix, whose next hop is resolved to a set of ECMP tunnel next hops with a static route in RTM or TTM or to IGP shortcuts in RTM
IPv4 BGP-labeled unicast routes whose next hop resolves to a set of tunnels in TTM
BGP-labeled IPv6 packets (6PE) resolving in TTM
This feature does not modify the route calculation: the same set of ECMP next hops is computed for a prefix. The feature also does not change the hash routine; only the spraying of the flows over the tunnel next hops is modified to reflect the normalized weight of each tunnel next hop.
Static route implementation supports ECMP over a set of equal-cost MPLS LSPs. The user can allow automatic selection or specify the names of the equal-metric MPLS LSPs in TTM to be used in the ECMP set. For more information, see Static route resolution using tunnels.