From mboxrd@z Thu Jan 1 00:00:00 1970 From: Igor Tsinman Subject: Re: NAT FROM public ip TO public ip Date: Thu, 06 Jan 2005 09:23:43 +0200 Message-ID: <41DCE77F.4020503@go-wlan.com> References: <10459.1105072608@www72.gmx.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <10459.1105072608@www72.gmx.net> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: netfilter-bounces@lists.netfilter.org Errors-To: netfilter-bounces@lists.netfilter.org Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Mario Ohnewald Cc: netfilter@lists.netfilter.org Mario Ohnewald wrote: >Hello List! > >This is a real easy question, but i will explain it in detail so that you >know what i am on about ;) > >I have two internet boxes, both have only one nic. >Box A is my root box. >Box B is a ftp server (where i am not admin, but i have an ftp account). > >Both, Box A and B have a public ip address. >You can NOT access the ftp server from the outside. >ONLY Box A can connect to that ftp server (Box B). > >So i though i could simply nat a connection through my Box A, to Box B. >If i connect from the real bad world, to my Box A, port 2121. Box A could >forward/NAT that to the internal ftp box. > >I have tried it with this rule: >$IPT -t nat -A PREROUTING -i eth0 -p tcp -d 123.123.123.123 -m helper >--helper ftp-2121 -j DNAT --to-destination 123.123.123.111 > >and > >modprobe ip_conntrack_ftp ports=21,2121 > > >But it looks like its not working. >I did a tcpdump -i eth0 -n host 123.123.123.111 > > >And no packages where transfered to the ftp box (123.123.123.111). >Any idea why? Am i going the right way at all? > >Thanks, Mario > > > You have to add an additional rule: $IPT -A FORWARD -p tcp -i eth1 -d 23.123.123.123 --dport 2121 -j ACCEPT For this example, eth0 is external and eth1 is internal. Cheers, Igor Tsinman igort@gonetworks.com