IPFW Firewall NAT inbound port-redirect

[Michael Sierchio]

Sorry for the naive question, but most of my old rulesets still use
natd, and I've only used built-in nat for outbound traffic.  I'd like
to redirect certain ports on certain addresses to the same ports on
internal (RFC1918) addresses.  The examples in the man page aren't
helpful, and the handbook still seems very natd-centric in its
examples.  Thanks in advance.

- Michael