Sharing connection - IPTABLES

Question

I've been trying to configure IPTABLES in my server so I can share the internet from the server with another machine. The server IP is 192.168.10.1 (eth0), the connection is coming from 192.168.0.6 (eth0:2), the client is 192.168.10.10 (eth1 in the machine). I've tried using the commands from

https://help.ubuntu.com/community/Internet/ConnectionSharing

with the correct changes, but I can't make it work, the client can ping 192.168.0.1 (where the internet is coming from), but it can't access the internet at all.

Server:

eth0 192.168.10.1 eth0:2 192.168.0.6 Currently has connection with both the client and the internet

Router:

192.168.0.1

Client:

eth1 192.168.10.10 Can ping both the router and the server

Solution

edit /etc/sysctl.conf and uncomment:

# net.ipv4.ip_forward=1

And the iptables part should look something like below, where eth0 is internet and eth1 is LAN:

iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE

iptables -A FORWARD -i eth1 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT

iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT

If you have 2 physical network interfaces in server then it should work, you cant use your server as internet gateway if it only has 1 physical interface

Comments

[cafebabe1991]

The questions seems quiet confusing. Are you talking about connecting to each other over ssh or just opening a port on your system so others can connect to it?

[Luck20]

Sorry, linked the wrong page, the correct one is help.ubuntu.com/community/Internet/ConnectionSharing

[Luck20]

Yes, I only have one physical interface, now I'm aware of the problem, thanks.

[Gillespie]

Are you sure you don't mean iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE? Otherwise you are NATing packets going into the private LAN, not coming out of it

[s.paszko]

iptables v1.6.1: unknown option "state"