Difference between revisions of "Create Custom NAT Instance in AWS VPC"

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(Created page with "== Purpose == Build a NAT instance using CentOS to propose internet access for private subnet in AWS VPC. <br>In this tutorial, we assume that we already have a VPC with pub...")
 
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[centos@nat-server ~]$ cat /proc/sys/net/ipv4/ip_forward
 
[centos@nat-server ~]$ cat /proc/sys/net/ipv4/ip_forward
 
1
 
1
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</pre>
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== Set Iptables for Masquerade ==
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 +
Issue iptables command below :
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 +
<pre>
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[centos@nat-server ~]$ iptables -t nat -A POSTROUTING -o eth0 -s 172.31.158.0/24 -j MASQUERADE
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</pre>
 +
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Edit the /etc/rc.local file to make masquerade will automatically enable at boot time :
 +
 +
<pre>
 +
[centos@nat-server ~]$ vi /etc/rc.local
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</pre>
 +
 +
And add this iptables command before "exit 0" :
 +
 +
<pre>
 +
...
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 +
iptables -t nat -A POSTROUTING -o eth0 -s 172.31.158.0/24 -j MASQUERADE
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exit 0
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 +
...
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</pre>
 +
 +
Run 'chmod +x /etc/rc.d/rc.local' to ensure the script will be executed during boot :
 +
 +
<pre>
 +
[centos@nat-server ~]$ chmod +x /etc/rc.d/rc.local
 
</pre>
 
</pre>

Revision as of 12:35, 14 November 2019

Purpose

Build a NAT instance using CentOS to propose internet access for private subnet in AWS VPC.
In this tutorial, we assume that we already have a VPC with public and prvate subnet like belo picture.

Preparation

[root@nat-server ~]# yum update

Dissable Source/Dest. Check for the NAT Server

Configure System

In /etc/sysctl.conf enable ip forwarding : 

[root@nat-server ~]# vi /etc/sysctl.conf

Add this : 

# For NAT Server
net.ipv4.ip_forward = 1

Reboot now for good measure : 

[root@nat-server ~]# reboot

Test our config : 

[centos@nat-server ~]$ cat /proc/sys/net/ipv4/ip_forward
1

Set Iptables for Masquerade

Issue iptables command below : 

[centos@nat-server ~]$ iptables -t nat -A POSTROUTING -o eth0 -s 172.31.158.0/24 -j MASQUERADE

Edit the /etc/rc.local file to make masquerade will automatically enable at boot time : 

[centos@nat-server ~]$ vi /etc/rc.local

And add this iptables command before "exit 0" : 

...

iptables -t nat -A POSTROUTING -o eth0 -s 172.31.158.0/24 -j MASQUERADE
exit 0

...

Run 'chmod +x /etc/rc.d/rc.local' to ensure the script will be executed during boot : 

[centos@nat-server ~]$ chmod +x /etc/rc.d/rc.local
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