Similar to the ibdiagnet command, the ibdiagpath command can perform some of the same tests for a particular route.
# ibdiagpath -v -l slid,dlid
slid is the LID of the source node.
dlid is the LID of the destination node.
The ibdiagpath.log file contains the log of the testing.
Switch Reference, ibdiagnet command
Switch Reference, ibdiagpath command