Hash-Based Forwarding (HBF) is an InfiniBand switch feature that enables selection of the switch outgoing port for statically routed packets based on the packet's parameters (ECMP like) as opposed to selection of the switch outgoing port based on Linear Forwarding Tables.
HBF configuration is done in the opensm.conf file (path: /opt/ufm/files/conf/opensm/opensm.conf).
For description of the possible HBF options, see https://enterprise-support.nvidia.com/s/article/Recommended-Topologies-for-Implementing-an-HPC-Cluster-with-NVIDIA-Quantum-InfiniBand-Solutions-Part-2.