Difference between revisions of "Set up Network Address Translation"

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(New page: To set up NAT, open a console and enter echo 1 > /proc/sys/net/ipv4/ip_forward iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE Category:Guides)
 
 
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To set up NAT, [[open a console]] and enter
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= Overview =
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  echo 1 > /proc/sys/net/ipv4/ip_forward
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Network address translation (NAT) is if you have a private network with private IP addresses and all these computers share access the internet via one computer. This computer, it can also be a cluster, is said to translate the network addresses between the private network and the internet.
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  iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
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 +
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                                                -----------------------------------------------------------
 +
                                              |                                                          |
 +
                                              |                          --------------                  |
 +
                                              |                        | internal    |                  |
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                                              |                        /| 172.16.0.43  |                  |
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                                              |                      /  --------------                  |
 +
                                        -------------                /                                    |
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                  ---------            | NAT-gateway |              /    --------------                  |
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                |internet |------------| 10.2.2.18  |            /    |  internal    |                  |
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                  ---------            | 172.16.0.1  |------------------| 172.16.0.42  |                  |
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                                        -------------                    --------------                  |
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                                              |                                                          |
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                                                -----------------------------------------------------------
 +
 
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= Set it up =
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To set up NAT ([[network]] address translation) on the NAT gateway, [[open a console]] and  
 +
* allow IP traffic forwarding on the NAT-gateway
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  [[echo]] 1 > /proc/sys/net/ipv4/ip_forward
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* tell the kernel on the NAT-gateway to forward traffic to the outgoing interface ''eth0'' and masquerade it, so it will put its own IP address into each packet's header:
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  iptables -t nat -A POSTROUTING -o <abbr title="outgoing interface">''eth0''</abbr> -j MASQUERADE
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= Test it =
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To test if it has worked, go to one of the internal computers and set the computer doing NAT as gateway, e.g. under Linux:
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route add default gw ''192.168.0.1''
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Then try to ping google's name server. If it works, you did it right:
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ping 8.8.8.8
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= See also =
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* [[set up a wireless accesspoint]]
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* [[Tunneling with OpenSSH]]
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* [http://www.nerdgrind.com/set-up-nat-with-linux-and-iptables-firewall/ set up NAT]
  
 
[[Category:Guides]]
 
[[Category:Guides]]

Latest revision as of 11:43, 18 June 2015

Overview

Network address translation (NAT) is if you have a private network with private IP addresses and all these computers share access the internet via one computer. This computer, it can also be a cluster, is said to translate the network addresses between the private network and the internet. 


                                               -----------------------------------------------------------
                                              |                                                           |
                                              |                          --------------                   |
                                              |                         | internal     |                  |
                                              |                        /| 172.16.0.43  |                  |
                                              |                       /  --------------                   |
                                        -------------                /                                    |
                 ---------             | NAT-gateway |              /    --------------                   |
                |internet |------------| 10.2.2.18   |             /    |  internal    |                  |
                 ---------             | 172.16.0.1  |------------------| 172.16.0.42  |                  |
                                        -------------                    --------------                   |
                                              |                                                           |
                                               -----------------------------------------------------------

Set it up

To set up NAT (network address translation) on the NAT gateway, open a console and

  • allow IP traffic forwarding on the NAT-gateway
echo 1 > /proc/sys/net/ipv4/ip_forward
  • tell the kernel on the NAT-gateway to forward traffic to the outgoing interface eth0 and masquerade it, so it will put its own IP address into each packet's header:
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

Test it

To test if it has worked, go to one of the internal computers and set the computer doing NAT as gateway, e.g. under Linux: 

route add default gw 192.168.0.1

Then try to ping google's name server. If it works, you did it right: 

ping 8.8.8.8

See also

Retrieved from "http://linuxintro.org/index.php?title=Set_up_Network_Address_Translation&oldid=15123"