The optional Format argument is an octet (00-FF) which
    specifies the value of each byte in the test data part of
    each loop message.  The default results in alternating 0
    and 1 bits (55).

    loop  [node node-id] mop client client-name -
          format octect [,optional arguments...]

    Address and Circuit information loop is required for the
    loop mop client command.  If the Client cannot provide
    default Address and Circuit information, then that
    information must be specified in the command.

    loop  [node node-id] mop client -
          address lan-address, -
          circuit circuit-name, -
          format octet [,optional arguments...]

    Examples:

    loop mop client lamchp -  ! Client gives Address and Circuit
          format ff

    loop mop client mynode -  ! Client gives default Address
         circuit fddi-1, -
         format 00