firewall/nat question: simple, but no example found

[Tetsuji "Maverick" Rai]

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Hi,

I've been using Linux and know iptables well, but I don't know ipfw
although I had been using FreeBSD for 3 years good old days w/o firewall
with dial up connection ;)  So here goes my question.

I am building a FreeBSD gateway at home.   It obtains an external IP
address from ISP dynamically using dhcp and I have two other boxes (and
some virtual boxes) internally using static private network addresses
(192.168.x.x).

I want to set up a firewall/nat so that

1. The gateway (also a web server) accepts tcp port 80 and (probably) 25
from outside. but incoming tcp/udp ports 1-1024,1043,10000 connections
are blocked.
2. Inside private network, nothing is blocked.

Isn't it so simple?  But I cannot find any nice examples...the default
rc.firewall contains examples using the static ip address, but not DHCP.
 I want to specify the interface not ip address.  BTW my external
interface is rl0 (dhcp) and the internal one is fxp0 (static).

Thanks in advance!
- --
Tetsuji 'Maverick' Rai
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