VMS Help LANCP, SET, DEVICE parameters, Qualifiers, /SPEED  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /SPEED=value

    Sets the speed of the LAN.

    For Token Ring, valid values are either 4 or 16, indicating
    4 megabits per second or 16 megabits per second. The default
    value for Token Ring is 16, unless the LAN adapter supports a
    nonvolatile mechanism for setting this parameter (as does the DEC
    Token Ring Controller 700).

    For Ethernet, valid values are either 10 or 100, which selects
    the 10 megabits per second Ethernet port or the 100 megabits per
    second Fast Ethernet port. The default for Ethernet is to sense
    automatically which type of port is connected and select the
    appropriate speed.