NAT rules are loaded by using the ipnat utility. The NAT rules can be stored
in any file on the system, but typically these rules are stored in /etc/ipnat.rules,
/usr/local/etc/ipnat.rules, or /etc/opt/ipf/ipnat.rules.
Rules can also be removed from the list instead of added by using the -r
command line option, but it is generally a safer idea to flush the rule set that you're
working on with -C and completely reload it when making changes. Any active
mappings are not affected by -C, and can be removed with -F.
NAT rules and active mappings can be examined with the -l command line option.
In summary, the easiest way to load a NAT rule set is ipnat -CF -f /etc/ipnat.rules.