HP-UX IPFilter Version 15.01 Administrator's Guide

For example (using the above NAT rules), if you wanted to
prevent all hosts in the 10.1.2.0/24 subnet from using NAT, you
might use the following rule with ipf:
block out on ppp0 from 10.1.2.0/24 to any
block in on ppp0 from any to 10.1.2.0/24
and use these with ipnat:
map ppp0 10.1.0.0/16 -> 209.23.1.0/28 portmap tcp/udp 10000:40000
map ppp0 10.1.0.0/16 -> 209.23.1.0/28 portmap
nat-setup 135