This article explains how to share the internet connection from one machine to other(s).
- The machine acting as server should have an additional network device
- That network device should be connected to the machines that are going to receive internet access. They can be one or more machines. To be able to share internet to several machines a switch is required. If you are sharing to only one machine, a crossover cable is sufficient
Using Udev#Setting static device names, name the network device connected to the other computer(s) as net0 and the network device connected to the internet as internet0.
Static IP address
Assign an static IPv4 address to the interface connected to the other machines. The first 3 bytes of this address cannot be exactly the same as those of another interface.
# ip link set up dev net0 # ip addr add 220.127.116.11/24 dev net0 # arbitrary address
To have your static ip assigned at boot, you can use netcfg.
Enable packet forwarding
Enter this command to temporaly enable packet forwarding:
/etc/sysctl.conf and add this line, which will make the previous change persistent after a reboot.
If you are using ipv6, use these lines:
Use iptables to enable NAT:
# iptables -t nat -A POSTROUTING -o internet0 -j MASQUERADE # iptables-save > /etc/iptables/iptables.rules # systemctl start iptables
You can set
iptables.service to auto start a boot.
Read the iptables article for more information.
Assigning ip addresses to the client pc(s)
If you are planning to regularly have several machines using the internet shared by this machine, then is a good idea to install a dhcp server.
If you are not planing to use this setup regularly, you can manually add an ip to each client instead.
Manually adding an ip
Instead of using dhcp, on each client pc, add an ip address and the default route:
ip addr add 18.104.22.168/24 dev eth0 ip link set up dev eth0 ip route add default via 22.214.171.124 dev eth0
Add a nameserver:
echo "nameserver <nameserver ip>" >> /etc/resolv.conf
You can figure out the address of the nameserver by looking into the
/etc/resolv.conf of the server, if its Internet connection is already established.
If you don't have a nameserver, you can use any of the free public DNS servers, which are relatively fast:
- Google Public DNS
Bracket notation must be used for IPv6 addresses in resolv.conf.
That's it. The client PC should now have Internet.
If you are able to connect the two PCs but cannot send data (for example, if the client PC makes a DHCP request to the server PC, the server PC receives the request and offers an IP to the client, but the client does not accept it, timing out instead), check that you don't have other Iptables rules interfering.