The cause of current operational state of the
port.
The current operational state of the port is shown by
the 'fcTrunkIfOperStatus'. This object will show
'none(2)' for all the 'fcTrunkIfOperStatus' values
except for 'down(2)'. It will show one of the values
from the 'FcIfOperStatusReason' textual convention
if 'fcTrunkIfOperStatus' is 'down(2)'.