This Unsigned64 is an aggregated fault bitmap rolled up onto this switch-side link record from any faults raised against it. It matters on the same internal chassis backplane link, but the record kept on the Fabric Interconnect (switch) side rather than the IOM/server side because it gives an admin a one-field summary of whether the fabric interconnect itself sees a problem with this backplane connection, independent of whatever the IOM side reports. A nonzero fltAggr on this link's fabric-interconnect side even while the matching ServerIntFIo object shows no faults would point specifically to a fabric-interconnect-side issue with this link, such as a port-level condition on the switch itself.