Library /sys$common/syshlp/tcpip$ucp_help.hlb SET, BOOTP, Qualifiers, /NETWORK_MASK  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /NETWORK_MASK=IP_address

    Required if you use subnets; otherwise optional.

    Specifies the part of the host field of an IP address identified
    as the subnet.

    The software calculates the default by setting the following:

    o  The bits representing the network field to 1

    o  The bits representing the host field to 0

    You can divide the host field into a site-specific subnetwork
    and a host field. If you use subnets, you must specify a subnet
    field.