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Re: set up NAT (network address translation) on local server



Robin Laing wrote:
Antonio Olivares wrote:
--- On Thu, 11/20/08, Christopher K. Johnson <ckjohnson gwi net> wrote:

From: Christopher K. Johnson <ckjohnson gwi net>
Subject: Re: set up NAT (network address translation) on local server
To: "Community assistance, encouragement, and advice for using Fedora." <fedora-list redhat com>
Date: Thursday, November 20, 2008, 10:27 AM
It appears from your email that there was an editing error
at the COMMIT or line after.
Perhaps instead of a line-end on those lines it has spaces
and wrapped them into one long line?
Could happen from copy and paste depending on
circumstances.
Check that each rule is on its own line.


I reset the iptables back to the original condition and added them, but still no joy :(


[root localhost ~]# gedit /etc/sysconfig/iptables & [1] 8516 [root localhost ~]# service iptables stop
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
iptables: Unloading modules:                               [  OK  ]
[root localhost ~]# service iptables restart
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules: Bad argument `iptables' Error occurred at line: 2 Try `iptables-restore -h' or 'iptables-restore --help' for more information. [FAILED] [root localhost ~]# service iptables stop
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Setting chains to policy ACCEPT: nat filter      [  OK  ]
iptables: Unloading modules:                               [  OK  ]
[root localhost ~]# iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT [1]+ Done gedit /etc/sysconfig/iptables [root localhost ~]# iptables -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT [root localhost ~]# iptables -A POSTROUTING -t nat -s 192.168.1.0/24 -o eth0 -j SNAT --to-source 10.154.19.210 [root localhost ~]# iptables-save
# Generated by iptables-save v1.4.1.1 on Thu Nov 20 13:14:50 2008
*nat :PREROUTING ACCEPT [5:692] :POSTROUTING ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A POSTROUTING -s 192.168.1.0/24 -o eth0 -j SNAT --to-source 10.154.19.210 COMMIT # Completed on Thu Nov 20 13:14:50 2008 # Generated by iptables-save v1.4.1.1 on Thu Nov 20 13:14:50 2008 *filter :INPUT ACCEPT [2483:1813687] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [2598:1049836] -A FORWARD -i eth1 -o eth0 -j ACCEPT -A FORWARD -i eth0 -o eth1 -m state --state RELATED,ESTABLISHED -j ACCEPT COMMIT # Completed on Thu Nov 20 13:14:50 2008 [root localhost ~]# service iptables restart
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Setting chains to policy ACCEPT: nat filter      [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules:                         [  OK  ]
iptables: Loading additional modules: ip_conntrack_netbios_[  OK  ]
[root localhost ~]# service dhcpd start Starting dhcpd: [ OK ]
[root localhost ~]#

The iptables get back to original state.  error in iptables-save ?/bug
[root localhost ~]# cat /etc/sysconfig/iptables
# Firewall configuration written by system-config-securitylevel
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 224.0.0.251 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT



Thanks,

Antonio


I fought with iptables on my desktop doing this and found a link that described and issue with Fedora resetting the iptables on each reboot. It provided a way to create an iptables modification init.d procedure for just this problem. It works like a dream.


Sorry I don't have the link as it is at home.

It's really simple.  When "service iptables start" is run at boot time,
the system runs

	iptables-restore </etc/sysconfig/iptables

to restore the configuration.  In /etc/sysconfig/iptables-config, if you
change the following lines to these:

	IPTABLES_SAVE_ON_STOP = "yes"
	IPTABLES_SAVE_ON_RESTART = "yes"

(by default they're set to "no"), you will cause the system to run

	iptables-save >/etc/sysconfig/iptables

when "system iptables stop|restart" is run ("restart" is really a "stop"
followed by a "start").  This will save any changes made to the running
rules by the iptables command before iptables is actually stopped.

You can run the above command manually after futzing with your config
using the iptables command to make sure they get saved, too.
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