NAT / ipfw / GW - FreeBSD 4.10 to Linux Private Network???

Sat Aug 14 20:48:08 PDT 2004

Hello All,

So with the help of all of you I have configure my FreeBSD 4.10 gateway.
I am able to ping, tracerout, ssh and call webpages with a fully
functioning DHCP client. I thank all of you from the bottom of my heart,
those of you that helped me out... its been hardwork and late nights (or
early mornings) building these computers from scratch and then
introducing them with Linux and FreeBSD OS's which I have only a
combined year of experience.

With that said I have come to the final component of my network... the
NAT component. I was trying to play around with it until I found out
that I really didn't know what I was doing... so here I am again.

I'm trying to configure one box through NAT via my FreeBSD gateway. I
figure after I do it once I'll be able to tweak it for the rest of my
machines. This is my set up

[internet] --------------------- [firewall/gateway] -- [ linux box ]
		24.199.105.0	-->	192.168.1.1 ->	192.168.1.3
		(   dc0   )		 (  txp0  )	(  eth0  )

I'm trying to get internet connection for my linux box, and I also want
all pop3, smtp and http passed to my linux box as well.  The freebsd box
is setup to be headless once I get this configured properly. In addition
I would like SSH2 to be able to tunnel from box to box as well as SSH2
outside my network with my Linux box.

I have attached my config files for ipfw.rules, rc.conf, and natd.conf
however natd.conf is where I am "lost" I don't exactly know the rules
for natd.conf. I reviewed my resources: "The Complete FreeBSD" by Greg
Lehey and "Absolute BSD" by Michael Lucas however there was not much on
the actual syntax. If someone could help me in these areas it would be
greatly appreciated.  Thanks in advance...

Hakim Z. Singhji
New York University
1st year Information Systems Management Student

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###############################
# RC.CONF FILE
###############################

############ Network ##########

gateway_enable="YES"
network_interfaces="dc0 txp0 txp1"
hostname="redgate.ath.cx"
ifconfig_dc0="DHCP"
ifconfig_txp0="inet 192.168.1.1/24"
ifconfig_txp1="inet 192.168.1.2/24"
natd_enable="dc0"
natd_flags="-s -u -f /etc/natd.conf"

############# IPFW ############

firewall_enable="YES"
firewall_script="/etc/rc.firewall"
firewall_type="/etc/ipfw.rules"
firewall_quiet="NO"
firewall_logging_enable="YES"

## Extra Firewalling Options ##

log_in_vain="YES"
tcp_drop_synfin="NO"
tcp_restrict_rst="YES"
icmp_drop_redirect="YES"

######## MISC RC Rules #########

...

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################################
# IPFW.RULES
################################

add 00100 allow ip from any to any via lo0
add 00101 deny ip from any to 127.0.0.0/8

# from man ipfw: allow only tcp connections I've created
add 00300 check-state
add 00301 deny tcp from any to any in established
add 00302 allow tcp from any to any out setup keep-state

# allow DNS/UDP Packets
add 00400 allow udp from 207.69.188.185 53 to any in recv dc0
add 00401 allow udp from 207.69.188.186 53 to any in recv dc0
add 00402 allow udp from 207.69.188.187 53 to any in recv dc0
add 00403 allow udp from any to any out 

# allow DHCP
add 00500 allow udp from any 68 to 24.29.99.105. 67 out via dc0
add 00501 allow udp from 24.29.99.105 67 to any 68 in via dc0

# uncomment rules 00502 and 00503 if ISP's DHCP server has problems
#add 00502 allow udp from any 68 to 255.255.255.255 67 out via dc0
#add 00503 allow udp from any 67 to 255.255.255.255 68 in via dc0

#allow some icmp types (codes not supported)
add 00600 allow icmp from any to any icmptypes 3

#allow source quench in and out 
add 00601 allow icmp from any to any icmptypes 4

#allow me to ping out and receive response back
add 00602 allow icmp from any to any icmp types 8 out
add 00603 allow icmp from any to any icmptypes 0 in

#allow me to run traceroute
add 00604 allow icmp from any to any icmptypes 11 in
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##################################
# NAT.CONF
##################################

# I'm not at all sure if this is ok for "diverting" these packets
# to my private network machines ip and port numbers???

redirect_port tcp 192.168.1.3:110 110 #pop3
redirect_port udp 192.168.1.3:110 110 #pop3
redirect_port tcp 192.168.1.3:25 25 #smtp
redirect_port udp 192.168.1.3:25 25 #smtp
redirect_port tcp 192.168.1.3:80 80 #http
redirect_port udp 192.168.1.3:80 80 #http

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