We are now facing the decision to use single bonded infiniband interface or use them separately (on the same subnet) managed by GI(actually 188.8.131.52) as multiple private interfaces for GI interconnect. Throughput of private interconnect is not a constraint in our case and the second infiniband interface is only for "backup - redundancy" purpose. Hardware is homogenous on both interfaces.
Having a network level bonding or having multiple interfaces for private interconnect is a personal choice and based on business requirement you can take call on the configuration. However, even if you do not choose network bonding Oracle has come up with a feature called HAIP from 11gR2 onwards, for network reduncdancy.
Ref: Grid Infrastructure Redundant Interconnect and ora.cluster_interconnect.haip (Doc ID 1210883.1)