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<p class=MsoNormal>Hi, <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’m a fairly solid linux user for what I need it to do
but recently I’ve been setting up a new SFF computer for my workplace
which is to handle squid and firewalling/port forwarding. My problems have
mainly arisen from the latter.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’ve been attempting to forward port 25 from this
firewall machine to our internal Email machine (192.168.email.IP:25) the
firewall has two interfaces one to eventually handle internal and one external
traffic however at this point both are connected to a switch for setup
(eventually an ADSL modem/router will handle the connection and forward all
ports directly to eth0). I’ve been using the following rules in various
combinations with various limited amounts of success:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Iptables –t nat –A PREROUTING –p tcp –dport
25 –j DNAT –to-destination 192.168.email.ip<o:p></o:p></p>
<p class=MsoNormal>Iptables –t nat –A OUTPUT –p tcp –m –dport
25 –j DNAT –to-destination 192.168.email.ip<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>With just the Prerouting nothing happens which isn’t
too much of a suprise, with the Output I can get to eth0:25 from the firewall
machine, but not from a networked laptop (same address range). Unfortunately
the latop doesn’t give me any useful error reporting, however when I
connect to the port via a ssh session on the firewall machine the following
message appears on the monitor attached to the machine itself:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>“NAT: no longer support implicit source local NAT<o:p></o:p></p>
<p class=MsoNormal> NAT: packet src 192.168.email.ip -> dst
192.168.ext.firewall”<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The external firewall nic is the one I am attempting to
connect to however the src and dst seem to be the wrong way around.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’m running Fedora Core 6, and I have been using
webmin the last few days, though the problem started before then, I simply
started using webmins linux firewall tools to try and keep any of my errors to
a minimum. Full copy of /etc/sysconfig/iptables incoming.....<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal># Generated by iptables-save v1.3.5 on Mon Sep 17 09:57:20
2007<o:p></o:p></p>
<p class=MsoNormal>*filter<o:p></o:p></p>
<p class=MsoNormal>:FORWARD ACCEPT [0:0]<o:p></o:p></p>
<p class=MsoNormal>:INPUT ACCEPT [0:0]<o:p></o:p></p>
<p class=MsoNormal>:OUTPUT ACCEPT [0:0]<o:p></o:p></p>
<p class=MsoNormal>-A FORWARD -p tcp -m tcp -d 192.168.42.188 --dport 25 -j
ACCEPT<o:p></o:p></p>
<p class=MsoNormal>-A INPUT -p tcp -m tcp --dport 25 -j ACCEPT<o:p></o:p></p>
<p class=MsoNormal>-A OUTPUT -p tcp -m tcp --dport 25 -j ACCEPT<o:p></o:p></p>
<p class=MsoNormal>COMMIT<o:p></o:p></p>
<p class=MsoNormal># Completed on Mon Sep 17 09:57:20 2007<o:p></o:p></p>
<p class=MsoNormal># Generated by iptables-save v1.3.5 on Mon Sep 17 09:57:20
2007<o:p></o:p></p>
<p class=MsoNormal>*nat<o:p></o:p></p>
<p class=MsoNormal>:PREROUTING ACCEPT [0:0]<o:p></o:p></p>
<p class=MsoNormal>:OUTPUT ACCEPT [0:0]<o:p></o:p></p>
<p class=MsoNormal>:POSTROUTING ACCEPT [0:0]<o:p></o:p></p>
<p class=MsoNormal>-A PREROUTING -p tcp -m tcp -i eth1 --dport 80 -j REDIRECT
--to-ports 3128<o:p></o:p></p>
<p class=MsoNormal>-A PREROUTING -p tcp -m tcp -i eth0 --dport 25 -j DNAT
--to-destination 192.168.42.2:25<o:p></o:p></p>
<p class=MsoNormal>-A OUTPUT -p tcp -m tcp --dport 25 -j DNAT --to-destination
192.168.42.2:25<o:p></o:p></p>
<p class=MsoNormal>COMMIT<o:p></o:p></p>
<p class=MsoNormal># Completed on Mon Sep 17 09:57:20 2007<o:p></o:p></p>
<p class=MsoNormal># Generated by webmin<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>(no mangle, some of the rules have been from sheer
desperation so if some of it looks like a walking talking contradiction it’s
just my madness creeping in).<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Any help greatly appreciated.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Matthew.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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