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87 lines
3.6 KiB
Markdown
87 lines
3.6 KiB
Markdown
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Turning a CentOS/RHEL 6 or 7 machine into a router
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======
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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.
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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.
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### Prerequisite
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**1-** A machine with either RHEL/CentOS 6 or 7 installed
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**2-** Two NICs to assign local IP address & WAN IP address respectively
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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
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**Ifcfg-en0s3 192.168.1.1** (LAN IP address)
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**Ifcfg-en0s5 10.1.1.1 ** (WAN IP address)
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**Note** - Change the interface name according to Linux distro being used.
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Now that we have what we need, we will move onto the setup
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### Step 1 Enabling IP forwarding
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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
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```
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$ sysctl -w net.ipv4.ip_forward=1
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```
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But this will not persist on system reboot. To make it survive a system reboot, open
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```
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$ vi /etc/sysctl.conf
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```
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& enter the following to the file,
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```
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net.ipv4.ip_forward = 1
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```
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Save file & exit. IP forwarding has now been enabled on the system.
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### Step 2 Configuring IPtables/Firewalld rules
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Next we need to start services of IPtables/firewalld on our systems to configure the NATting rule,
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```
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$ systemctl start firewalld (For Centos/RHEL 7)
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$ service iptables start (For Centos/RHEL 6)
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```
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Next step is to configure the NATting rule on the firewall. Run the following command,
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```
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CentOS/RHEL 6
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$ iptables -t nat -A POSTROUTING -o XXXX -j MASQUERADE
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$ service iptables restart CentOS/RHEL 7
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$ firewall-cmd -permanent -direct -passthrough ipv4 -t nat -I POSTROUTING -o XXXX -j MASQUERADE -s 192.168.1.0/24
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$ systemctl restart firewalld
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```
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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.
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### Step 3 Configuring the client machine
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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,
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**$ ping google.com
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**
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We can also check by browsing websites via our web browser.
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--------------------------------------------------------------------------------
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via: http://linuxtechlab.com/turning-centosrhel-6-7-machine-router/
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作者：[][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:http://linuxtechlab.com
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[1]:https://www.facebook.com/linuxtechlab/
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[2]:https://twitter.com/LinuxTechLab
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[3]:https://plus.google.com/+linuxtechlab
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