NetBSD-5.0.2/regress/sys/kern/ipf/regress/ni1.nat

map df0 from 2.2.2.2/32 port 20000 >< 25000 to any -> 6.6.6.8/32 portmap udp 2000:2500 sequential
map df0 from 2.2.2.2/32 port 2000 >< 2500 to any -> 6.6.6.7/32 portmap udp 20000:25000 sequential
map df0 from 2.2.2.2/32 to any -> 6.6.6.6/32