set up NAT (network address translation) on local server

[Robin Laing]

Antonio Olivares wrote:
> --- On Thu, 11/20/08, Christopher K. Johnson <ckjohnson at gwi.net> wrote:
> 
>> From: Christopher K. Johnson <ckjohnson at gwi.net>
>> Subject: Re: set up NAT (network address translation) on local server
>> To: "Community assistance, encouragement, and advice for using Fedora." <fedora-list at 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 at localhost ~]# gedit /etc/sysconfig/iptables &            
> [1] 8516                                                       
> [root at localhost ~]# service iptables stop
> iptables: Flushing firewall rules:                         [  OK  ]
> iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
> iptables: Unloading modules:                               [  OK  ]
> [root at 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 at localhost ~]# service iptables stop
> iptables: Flushing firewall rules:                         [  OK  ]
> iptables: Setting chains to policy ACCEPT: nat filter      [  OK  ]
> iptables: Unloading modules:                               [  OK  ]
> [root at localhost ~]# iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT [1]+  Done                    gedit /etc/sysconfig/iptables       
> [root at localhost ~]# iptables -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT                                                          
> [root at localhost ~]# iptables -A POSTROUTING -t nat -s 192.168.1.0/24 -o eth0 -j SNAT --to-source 10.154.19.210                                          
> [root at 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 at 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 at localhost ~]# service dhcpd start                            
> Starting dhcpd:                                            [  OK  ]
> [root at localhost ~]#
> 
> The iptables get back to original state.  error in iptables-save ?/bug 
> 
> [root at 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.

-- 
Robin Laing