From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Subject: Re: forwarding traffic from one port to another on the same box Date: Wed, 28 Jan 2004 07:50:43 -0500 Sender: netfilter-admin@lists.netfilter.org Message-ID: References: <200401280549.i0S5nqmK030255@server5.bandwidthco.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200401280549.i0S5nqmK030255@server5.bandwidthco.com> Errors-To: netfilter-admin@lists.netfilter.org List-Help: List-Post: List-Subscribe: , List-Id: List-Unsubscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: netfilter@lists.netfilter.org Mark E. Donaldson wrote: > Andrew - your DNAT rule looks fine to me and it should work. I really > think your problem is the first rule, even though the error is apparently > charged to the second rule. I think what you need to do is change the first > rule to -A to the INPUT chain and not the forward chain and it should work. > The packet is not being forwarded, but is rather destined to the same NIC - > so it should be the INPUT chain. Try that and see if it does the trick. If > not, holler again cause there are many with greater expertise on this list > than me. Thanks for the advice but it's a no-go. I get the same error, 'Invalid argument', from the PREROUTING command if I use INPUT instead of FORWARD in the first command. I also tried replacing the DNAT target in the second command with REDIRECT. It didn't help. Andrew > > -----Original Message----- > From: netfilter-admin@lists.netfilter.org > [mailto:netfilter-admin@lists.netfilter.org] On Behalf Of Andrew > Sent: Tuesday, January 27, 2004 6:38 PM > To: netfilter@lists.netfilter.org > Subject: forwarding traffic from one port to another on the same box > > I would like to forward all tcp traffic arriving on a particular port to > another port on the same machine. This has worked for me in the past but I > can't get it working on my current machine. > > Here are the two commands I'm using to try to create the forward. > > iptables -I FORWARD -p tcp -d 192.168.10.34 --dport 26 -j ACCEPT > > iptables -t nat -A PREROUTING -p tcp -i eth0 -s 0/0 -d 192.168.10.34 --dport > 26 -j DNAT --to 192.168.10.34:25 > > The first command is accepted but the second command results in an 'Invalid > argument' error. > > The computer has only one interface, eth0. Here are its particulars: > Mandrake Linux 9.2 > Iptables 1.2.8 > kernel 2.4.24 patched with super-freeswan 1.99.8 > > The value of /proc/sys/net/ipv4/conf/eth0/forwarding is 0. Changing it to 1 > has no impact. > The value of /proc/sys/net/ipv4/conf/eth0/rp_filter is 0. > > I hope someone out there has some ideas about what's going on because I'm > all out. > > Andrew > > > > > >