Overview of Hierarchical ECMP Groups on QFX5200 Switches
Starting with Junos OS Releases 15.1X53-D30 and 17.2R1, QFX5200 switches support hierarchical equal-cost multipath (ECMP) groups.Hierarchical ECMP is enabled by default and provides for two-level route resolution automatically through the Packet Forwarding Engine. Two-level route resolution through ECMP groups enhances load balancing of traffic. The partition of hierarchical ECMP groups is fixed and cannot be modified. As a result, if groups designated for one type of prefixes, for example, overlay routes are not used, they cannot be designated for use by other types of traffic.
Starting with Junos OS Releases 15.1X53-D210 and 17.2R1, you can disable hierarchical ECMP groups at system start time on QFX5200 switches. Doing so makes all the ECMP groups available for route resolution for all types of prefixes, effectively increasing the number of ECMP groups. To disable hierarchical ECMP, include no-hierarchical-ecmp at the [edit forwarding-options] hierarchy level. Disabling hierarchical ECMP causes the Packet Forwarding Engine to restart.