Set up NAT on NetBSD

In order to enable packet forwarding, you should add this to /etc/sysctl.conf:

sysctl -w net.inet.ip.forwarding=1

(or enable ip forwarding when compiling the kernel)

Then, add this line to /etc/ipnat.conf:

map re0 192.168.1.0/24 -> 0/32

re0 is the name of your external etherned card.
Also, do not forget to add ipnat="YES" to your /etc/rc.conf.