A bit array that contains the oper-status
of the ports in the device.  2 bits are used
for each port.  The high order 2 bits of the
first octet represent port #0, the next two
bits are used for port #1, etc.  The status
is encoded with the following scheme :

value   meaning
-----   -------
  0     no-link (admin=up, oper=down)
  1     up      (admin=up, oper=up)
  2     down    (admin=down, oper=down)
  3     testing (admin=test, oper=test)