re nat masquerade router

Alexander Dalloz alexander.dalloz at
Tue Jun 15 19:26:00 UTC 2004

Am Di, den 15.06.2004 schrieb fedora um 20:51:

> Thanks for your help so far-
> still no luck with the Host web browser.
> 1_ How should I enter that last -s !?
> #"iptables -A INPUT -s ! -j DROP "  ...?

see below ...

> d) flushed rules and reset, without the "-s !"
> # iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
> # iptables -A FORWARD -s -j ACCEPT
> # iptables -A FORWARD -d -j ACCEPT

Just as a question: the # are just in your mail? Hope so!

Leave away line 2 and 3. Just use the POSTROUTING rule and none for
FORWARD, given that the FORWARD policy is set to accept.

> anything else I should try?
> Or go straight to another tool, as others have suggested?

As a general rule: start with simple setups! Do not more with iptables
as needed. So use the MASQUERADE in POSTROUTING nat table and all else
on accept - for the initial function testing. Later you can go through
and close things.

Question: how is your router connected to the internet? Try

echo 0 > /proc/sys/net/ipv4/tcp_ecn

Maybe you are hit by a broken DSL router/modem which does not handle ECN
proper. Maybe you must use mssclamping on the router:

iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS

> Chris


P.S. please strip your quotes and do not top-post! thanks

Alexander Dalloz | Enger, Germany | GPG key 1024D/ED695653 1999-07-13
Fedora GNU/Linux Core 2 (Tettnang) on Athlon CPU kernel 2.6.6-1.435 
Serendipity 21:12:07 up 17:39, 8 users, 1.32, 0.47, 0.27 
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