[gentoo-user] Re: iptables question

[James <wireless@tampabay.rr.com>]

Dmitry S. Makovey <dmitry <at> athabascau.ca> writes:

> somewhat offtopic, but since I need any help I can get:

> how do I redirect trafic from outward facing interface 
> (192.168.1.114:80) to loopback device (127.0.0.1:80) ?

> my most obvious trick:
> iptables -t nat -A PREROUTING -p tcp -d 192.168.1.114 --dport 80 \
> 	-j DNAT --to 127.0.0.1:80
> and 
> echo 1 > /proc/sys/net/ipv4/ip_forward
> didn't help. Machine which is opening connection is hanging there 
> indefinitely...

> what did I miss?


Well, let me start off by saying that I'm still learning the
details of iptables.....

An excellent book has been recommended and I can confirm it is wonderful:
"Linux Firewalls Third Edition" 2005. by Steve Suehring and Robert L. Ziegler.
Novell press.

There are many examples covering forwarding, port redirection, dmz's and
proxies. It's hard to tell exactly what you are doing, or what you want to do.

>From the book: Enabling the loopback Interface page 111
"
Local services rely on the loop back network interface. After the system boots,
the systems's default policy is to accept all packets. Flushing any pre existing
chains has no effect. However, if the firewall is being reinitialized and had
previously used a deny-by-default policy, the drop policy would still be in
effect. Without any acceptance firewall rules, the loopback interface would
still be inaccessible. Because the loopback interface is a local, internal
interface, the firewall can allow loopback traffic immediately:

#for unlimited traffic on the loopback interface
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT
"

Granted this is related to an example in the book, but hopefully it helps.
If you get frustrated, send me private email, maybe I can help. I will try.
Some folks on the list do not believe that direct control of iptables is
wise. I desent. Knowledge of iptables is of extreme value, but difficult 
to master. I'd like to see many example of iptable for 2.6 kernels published.
Updated material on iptables + 2.6 kernels, is scarcely available on the net.

hth,
James




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