Linux - Turn Computer Into Router for Internal Network


For this, I am using a Ubuntu computer with two ethernet cards.

  • eth0 connects to the internet on a DHCP connection
  • eth1 connects to a switch which all the other computers on the local network are connected to.
  • eth0 has ip 192.168.1.x where x can change
  • eth1 set to static ip as it will be the gateway.
  • All other computers on the network have ips set manually to 192.168.2.x with gateway set to
  • In network manager, eth1 connection set to with gateway 192.168.1.x which matches the ip of eth0


    Enter the following commands each time computer starts:

    sudo iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE
    sudo iptables --append FORWARD --in-interface eth1 -j ACCEPT
    You will need to allow packet forwarding.
    To do this in ubuntu, edit the /etc/sysctl.conf file and uncomment the line shown here (remove the # at the front)
    Run the following command:
    echo 1 > /proc/sys/net/ipv4/ip_forward


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