IPFW Firewall NAT inbound port-redirect

[Dan Nelson]

In the last episode (Jul 11), Michael Sierchio said:
> 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.

I use this at the top of my /etc/ipfw.conf file (re0.2 is the interface
corresponding to my internet connection) :

nat 123 config if re0.2 log same_ports redirect_port tcp 10.0.0.3:22 22 
add nat 123 ip from any to any via re0.2

, which redirects incoming port 22 connections to 10.0.0.3.  If you want to
redirect more ports, add more "redirect_port tcp host:port port" expressions
to the end of your nat line.  I believe you can run the nat config command
manually with a new list (as in "ipfw nat 123 ...") to add/remove entries
dynamically.  I'm not at home to try it, and don't want to risk losing my
remote connection if I mess up :)

-- 
	Dan Nelson
	dnelson at allantgroup.com