Port operation mode. Only the HDX and FDX modes can be
auto detected. Note, that passive-probe(7) mode can not be
set with this object. The passive-probe(7) mode is set
automatically when a passive probe is defined in the
ciscoTsPassiveProbeTable. Note also that ri-ro(6) is only
valid for ports 19, 20 (Catalyst 3900), and ports on a fiber
module.