Difference between revisions of "Set up Network Address Translation"
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| − | + | ----------------------------------------------------------- | |
| − | + | | | | |
| − | + | | -------------- | | |
| − | + | | | internal | | | |
| − | + | | /| 172.16.0.43 | | | |
| − | + | | / -------------- | | |
| − | + | ------------- / | | |
| − | + | --------- | NAT-gateway | / -------------- | | |
| − | + | |internet |------------| 10.2.2.18 | / | internal | | | |
| − | + | --------- | 172.16.0.1 |------------------| 172.16.0.42 | | | |
| − | + | ------------- -------------- | | |
| − | + | | | | |
| − | + | ----------------------------------------------------------- | |
= Set it up = | = Set it up = | ||
| − | To set up NAT ([[network]] address translation), [[open a console]] and | + | To set up NAT ([[network]] address translation) on the NAT gateway, [[open a console]] and |
| − | * allow IP traffic forwarding | + | * allow IP traffic forwarding on the NAT-gateway |
[[echo]] 1 > /proc/sys/net/ipv4/ip_forward | [[echo]] 1 > /proc/sys/net/ipv4/ip_forward | ||
| − | * tell the kernel to forward traffic to the outgoing interface ''eth0'' and masquerade it, so it will put its own IP address into each packet's header: | + | * 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 | + | iptables -t nat -A POSTROUTING -o <abbr title="outgoing interface">''eth0''</abbr> -j MASQUERADE |
= Test it = | = Test it = | ||
Latest revision as of 11:43, 18 June 2015
Contents
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
