Weighted ECMP Support for LDP

The router supports weighted ECMP in cases where LDP resolves a FEC over an ECMP set of direct next hops corresponding to IP network interfaces, and where it resolves the FEC over an ECMP set of RSVP-TE tunnels. See Weighted Load Balancing for LDP over RSVP for information about LDP over RSVP.

Weighted ECMP for direct IP network interfaces uses a load-balancing-weight configured under the config>router>ldp>interface-parameters>interface context. Similar to LDP over RSVP, Weighted ECMP for LDP is enabled using the weighted-ecmp command under the config>router>ldp context. If the interface becomes an ECMP next hop for an LDP FEC, and all the other ECMP next hops are interfaces with configured (non-zero) load-balancing weights, then the traffic distribution over the ECMP interfaces is proportional to the normalized weight. Then, LDP performs the normalization with a granularity of 64.

If one or more of the LDP interfaces in the ECMP set does not have a configured-load-balancing weight, then the system falls back to ECMP.

If both an IGP shortcut tunnel and a direct next hop exist to resolve a FEC, LDP prefers the tunneled resolution. Therefore, if an ECMP set consists of both IGP shortcuts and direct next hops, LDP only load balances across the IGP shortcuts.

Note: