VMS Help LANCP, SET, NODE, Qualifiers, /V3  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /V3
       /NOV3

    Indicates that only MOP Version 3 formatted messages are to be
    used for downline load purposes, regardless of the requested
    format. This allows systems to load that have a problem with MOP
    Version 4 booting. This qualifier causes the requesting node to
    fail over from MOP Version 4 to MOP Version 3 when no response
    has been made to a MOP Version 4 load request.

    If you do not specify the /V3 qualifier, the setting remains
    unchanged. The /NOV3 qualifier clears the setting.