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+Turning a CentOS/RHEL 6 or 7 machine into a router
+======
+In this tutorial we are going to learn to convert RHEL/CentOS 6 & 7 machines into a router by using NATting. Router as we know is layer 3 networking device that is used to connect 2 or more networks i.e. either connecting LAN to WAN or LAN to LAN etc. Router devices are quite expensive & especially for small organizations, that might be a reason for concern. So rather than using a dedicated Hardware, we can use any Linux machine & convert it into a router.
+We will be discussing process for both RHEL/CentOS 6 & 7\. But before we do that, let's discuss the things we will be needing for our setup.
+
+### Prerequisite
+
+**1-** A machine with either RHEL/CentOS 6 or 7 installed
+**2-** Two NICs to assign local IP address  & WAN IP address respectively
+
+We must assign IP address to both network interface cards, one IP should be for local area network (information regarding it will be provided by our Network administrator) & other IP should be to access internet, information for WAN IP will be provided by ISP. For example
+
+ **Ifcfg-en0s3 192.168.1.1** (LAN IP address)
+**Ifcfg-en0s5 10.1.1.1 ** (WAN IP address)
+
+ **Note** - Change the interface name according to Linux distro being used.
+
+Now that we have what we need, we will move onto the setup
+
+### Step 1 Enabling IP forwarding
+
+Firstly we will enable IP forwarding on the machine. Process of doing same is same in both RHEL/CentOS 6 & 7\. To enable IP forwarding, run
+
+```
+$ sysctl -w net.ipv4.ip_forward=1
+```
+
+But this will not persist on system reboot. To make it survive a system reboot, open
+
+```
+$ vi /etc/sysctl.conf
+```
+
+& enter the following to the file,
+
+```
+net.ipv4.ip_forward = 1
+```
+
+Save file & exit. IP forwarding has now been enabled on the system.
+
+### Step 2 Configuring IPtables/Firewalld rules
+
+Next we need to start services of IPtables/firewalld on our systems to configure the NATting rule,
+
+```
+$ systemctl start firewalld (For Centos/RHEL 7)
+$ service iptables start  (For Centos/RHEL 6)
+```
+
+Next step is to configure the NATting rule on the firewall. Run the following command,
+
+```
+CentOS/RHEL 6
+$ iptables -t nat -A POSTROUTING -o XXXX -j MASQUERADE
+$ service iptables restart CentOS/RHEL 7
+$ firewall-cmd  -permanent -direct -passthrough ipv4 -t nat -I POSTROUTING -o XXXX -j MASQUERADE -s 192.168.1.0/24
+$ systemctl restart firewalld
+```
+
+Here, **XXXX** is the name of the network interface with the WAN IP address. This completes configuration of Linux machine as router, next we will test our router after configuring a client machine.
+
+### Step 3 Configuring the client machine
+
+To test the router, we need to assign the internal (LAN) IP address as gateway on our client machine, its 192.168.1.1 in our case. So whether using a Windows machine or linux machine as client, make sure that we have 192.168.1.1 as our gateway. Once that's done, open terminal/CMD run a ping test against a website to make sure that internet is accessible on client machine,
+
+ **$ ping google.com
+**
+
+We can also check by browsing websites via our web browser.
+
+
+--------------------------------------------------------------------------------
+
+via: http://linuxtechlab.com/turning-centosrhel-6-7-machine-router/
+
+作者：[][a]
+译者：[译者ID](https://github.com/译者ID)
+校对：[校对者ID](https://github.com/校对者ID)
+
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+
+[a]:http://linuxtechlab.com
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