Internet Connection Sharing using iptables
Written by BinnyVA on April 16, 2007 – 4:26 pm -
It is very easy to setup an internet connection sharing in Linux system using iptables. This method can be used to share an internet connection from a Linux system(I used Fedora Core 6, but it should work on other distributions that support iptables). Another method of doing this is using a proxy server like squid.
Enable IP forwarding
Run as root
sysctl -w net.ipv4.ip_forward=1
To enable it in system startup, edit the file /etc/sysctl.conf and set
net.ipv4.ip_forward = 1
iptables
Run command as root
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
service iptables saveConfiguration
The configuration should be like this
Router
Connected to the internet provider
IP : 192.168.1.1
Internet Connected System
eth0 (LAN Card 1)
Connected to router
- IP : 192.168.1.10
- Netmask : 255.255.255.0
- Gateway : 192.168.1.1 (IP of the router)
eth1 (LAN Card 2)
Connected to the other system
- IP : 192.168.0.20 (Not the same network as the first card)
- Netmask : 255.255.255.0
- Gateway : 192.168.1.1 (IP of the router)
Second System
LAN Card connected to the first system
- IP : 192.168.0.30
- Netmask : 255.255.255.0
- Gateway : 192.168.0.20 (IP of the second Card in the first system)
Disclaimer
Linux networks is not a subject I am an expert on. So take my advice with a pinch of salt. The above procedure worked for me. YMMV.
Status
Some results of various commands are shown here. Check to see if it matches the result on your system.
# iptables -t nat -L POSTROUTING
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
MASQUERADE all — anywhere anywhere
# cat /proc/sys/net/ipv4/ip_forward
1# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
del.icio.us | Digg it | Furl | ma.gnolia | reddit | StumbleUpon |
Posted in Command Line, Fedora, Networking, Tutorials |
July 4th, 2007 at 7:48 pm
Well works on Fedora 5 and Fedora 6, but not on Fedora 7
July 5th, 2007 at 11:05 am
@flape
I use Fedora 7 - it works for me here. I had a bit of trouble setting it up at first - but in a few attempts it worked fine.
July 9th, 2007 at 12:46 pm
Hi
Can anbody tell if i share internet through this. then how can i do port forwarding for VNC and WEB Server located on windows client. what rules should be add in IPtables
August 23rd, 2007 at 2:32 am
Its not working on F7 any help please
October 23rd, 2007 at 2:16 am
Worked a dream. Ran the linux commands and it worked straight away - Fedora Core 7 with Windows clients.
Many many thanks!
October 26th, 2007 at 2:43 am
I tried it on fedora 7 (kernel 2.6.21). It didn’t work… Is there something else I need to download and install?
October 26th, 2007 at 1:45 pm
Hi
I tried it on my fedora 7 but didn’t worked
i didn’t get which router address we need to add?
November 21st, 2007 at 8:40 pm
Hi guys, nice tutorial, but i’m wondering if a different setup would still work. This is my current system:
- 1 external wireless router that shares the internet connection to the entire building (and to which I have no access to and uses DHCP to provide IPs to the clients);
- 1 server machine with 1 wireless card (connecting to the external router (again, DHCP)), and one internal (wired) network card, which I would setup with a static IP address;
- 1 wireless router (my own, full access), which I can connect to the server’s static IP network card;
- 1 laptop, which I wish to connect to the internal router and still have internet from the external router.
Is this possible, and if so, how do I set it up?
Thanks in advance,
Pedro
November 26th, 2007 at 11:53 am
please help me I would to setup and configuration internet server by IP table and web server and send mail Server on linux redhat Enterprise 4 or fedora 3 or 5
please help step by step ditail
November 27th, 2007 at 7:03 pm
Hi,
I m trying with fedora 8 but its not happening please help.
November 27th, 2007 at 7:03 pm
Hi,
I m trying with fedora 8 but its not happening please help.
vijay
November 27th, 2007 at 9:14 pm
@Vijay
I now have Fedora 8 - it worked perfectly.
December 29th, 2007 at 8:35 am
BinnyVA: what did u do on fedora 8 to make it work
December 29th, 2007 at 12:36 pm
@Joshua
Just follow the given instructions - it worked without any trouble for me.
March 7th, 2008 at 7:57 pm
This is real pretty cool im using Centos 5 and Fedora 8 it work fine
March 10th, 2008 at 8:41 pm
I’ve done it before and it is easy so there is nothing wrong with your advice thanks for taking the time to write them so clearly.
May 31st, 2008 at 8:34 pm
Is there anyone who knows how to set up this in similar situatuion: My laptop is connected to internet via eth1, but eth1 is ethernet emulation card and eth0 is other notebook.