subnet_group name address address_list mask subnet_mask
name is the name of the subnet group.
address_list is the list of networks to be included in this group. If entered as names, networks listed must be defined in the /etc/hosts file or the /etc/networks file.
subnet_mask is the subnet mask in dot format. You cannot use the + style of specifying a netmask.
subnet_group grp_nets address 129.xxx.yyy.0, plum mask 225.225.225.0