Configure Linux as a Router

Routing is forwarding data traffic between two or more computer networks according to given routing rules. Router perform this action which is connected to two or more data lines from different networks. When a data packet comes in on one of the lines, the router reads the network address information in the packet to determine the ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.


To reach internet for the PC or Laptop in above network, Linux box has to be configured as a router. It should route internal traffic to ISP router and internet traffic back to local network. We have two different methods to do this.

Method 1. NAT local network from Linux box

 This can be easily done with just a simple configuration on your Linux box. First you need to enable ip forwarding in your kernel parameters and then adding a NAT rule to iptables as follows.

echo 1 > /proc/sys/net/ipv4/ip_forward 
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A FORWARD -i eth0 -o eth1 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT

 you can add bellow line to /etc/sysctl.conf to make your nat rule permanent after reboot

net.ipv4.ip_forward = 1

You don't need to add any aditional routing entry to your routing table in this method because your internal network trafic will be NATed at the Linux router and go outside with the source ip of interface eth0. As we don't have specify the ip address when applying NAT rule, you can even use dynamic ip for outside interface(eth0) as target MASQUERADE used.


Method 2. Add Static route to ISP router

In this method you have to add a static route to your ISP router/firewall so that return traffic to 192.168.10.0/24 will be routed via the eth0 interface of Linux box.

Comments

Post a Comment

Popular posts from this blog

Installing and Configuring ndpi-netfilter for traffic controlling on ubuntu

nDPI is a ntop-maintained superset of the popular OpenDPI  library. Lots of projects have been done using this NDPI( Open and Extensible LGPLv3 Deep Packet Inspection Library ).  nDPI is used for application-layer detection of protocols, regardless of the port being used. This means that it is possible to both detect known protocols on non-standard ports (e.g. detect http non ports other than 80), and also the opposite (e.g. detect Skype traffic on port 80). This is because nowadays the concept of port=application no longer holds. List of protocols that can be detected using ndpi can be seen on ndpi page here.( http://www.ntop.org/products/deep-packet-inspection/ndpi/ ) Here i explain how to set up your own traffic controller using ndpi-netfilter which is very handy open project on github. Here we are setting it on on ubuntu 14.04LTS or newer as a linux kernel module and use with linux iptables.  If you want to setup it on RedHat/CentOS follow this sepa...
Read more

installing and configuring ndpi-netfilter for traffic controlling on RedHat/CentOS 7

nDPI is a ntop-maintained superset of the popular OpenDPI  library. Lots of projects have been done using this NDPI( Open and Extensible LGPLv3 Deep Packet Inspection Library ).  nDPI is used for application-layer detection of protocols, regardless of the port being used. This means that it is possible to both detect known protocols on non-standard ports (e.g. detect http non ports other than 80), and also the opposite (e.g. detect Skype traffic on port 80). This is because nowadays the concept of port=application no longer holds. List of protocols that can be detected using ndpi can be seen on ndpi page here.( http://www.ntop.org/products/deep-packet-inspection/ndpi/ )   Here i explain how to set up your own traffic controller using ndpi-netfilter which is very handy open project on github. Here we are setting it on on RedHat/CentOS 7 as a linux kernel module and use with linux iptables.  If you want to setup it on Ubuntu follow this sep...
Read more

Configuring Check Point SSL Network Extender on Ubuntu 14.04/10

Image
Configuring Check Point SSL network extender on windows will not be a problem, but configuring on linux may really a big problem if you couldn't install necessary dependencies and plugins. I, here describe how it was properly install on Ubuntu 14.04/10 and Linux Mint 17.2. I expect other Linux distributions will support this method. Follow the bellow steps. 1. You need to update the Ubuntu system first. use software updater or type the bellow command on terminal.   sudo apt-get update  sudo apt-get upgrade  sudo apt-get dist-upgrade  sudo apt-get autoclean 2. install JDK and icedTea plugin. you need to install jdk 6, because check point extender will not support for java version 7 and will give an error as "java unavailable".  sudo apt-get install openjdk-6-jre openjdk-6-jdk icedtea-plugin 3. Install necessary libraries.  sudo apt-get install libpam0g:i386 libx11-6:i386 libstdc++5:i386 4. restart the Ubuntu so that the changes to be t...
Read more