If your users use OpenBSD and have a 'bge' NIC you create a proper "/etc/hostname.bge0" file.
Code:
$cat /etc/hostname.bge0
#dhcp NONE NONE NONE
inet 192.168.222.20 255.255.255.0 NONE
!ifconfig bge0 media 100baseTX mediaopt full-duplex
See
hostname.if(5)
Or you set up a local DHCP server
But I still don't understand why you insist on using public IP addresses