Performs a loop operation with another system.

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

    If an Address is not supplied in the command on a LAN circuit,
    then the Client argument must be specified so the address
    information can be obtained from the MOP Client database.

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

    Optional arguments for this loop mop circuit command are:
    Assistance Type, Assistant Address, Assistant System, Count,
    Format, and Length.

    Examples:

    loop mop circuit csmacd-1 address 08-00-2b-00-13-4F

    loop mop circuit fddi-1 client mynode ! Client gives Address