How do I route internet in from wlan0 and out through eth0 in debian/centOS?

slacker_ · 01-30-2014, 04:47 AM

I've tried doing this by blackboxing it, didn't work out well. Tried googling, and didn't come up with much of anything that was helpful.

Essentially I want to be able to take the internet access I have through wifi, and pass it through a traffic filter and out the ethernet connection to a switch or directly to another system. Ie, use my laptop to access the internet via wifi, and provide that access to another system(s) over ethernet. I'd prefer a method that doesn't require some third-party application, and doesn't rely on a GUI, to the extent possible.

I've never done anything like this so I'll really need a step by step, newbie-friendly format if that's doable.

I'm using debian on a thinkpad t60p, but I dualboot with centOS so being able to do it in both will be necessary.

myatthu · 01-30-2014, 05:37 AM

I think below is relevant for you. For your case, eth1 at this document will be wlan0 I guess

http://www.cyberciti.biz/faq/rhel-fe...sharing-howto/

slacker_ · 01-30-2014, 04:50 PM

Quote:

Originally Posted by myatthu

I think below is relevant for you. For your case, eth1 at this document will be wlan0 I guess

http://www.cyberciti.biz/faq/rhel-fe...sharing-howto/

So according to this, my internal is eth0 and external is wlan0?

Now, while this is brilliant, do you know if this method works for debian?

myatthu · 01-30-2014, 08:03 PM

Yes. According to your initial post, eth0 is internal and wlan0 is wan.
For debian flavour, iptables rules are sane but network interfaces config file will be different.
Pls refer below excellent guide for debian flavour

http://www.debuntu.org/iptables-how-to-share-your-internet-connection/

slacker_ · 01-30-2014, 08:20 PM

Quote:

Originally Posted by myatthu

Yes. According to your initial post, eth0 is internal and wlan0 is wan.
For debian flavour, iptables rules are sane but network interfaces config file will be different.
Pls refer below excellent guide for debian flavour

http://www.debuntu.org/iptables-how-...et-connection/

That's interesting that the same method won't work with debian because the "sysctl.conf" exists in debian as well. Do they do different things between the two OSes?

slacker_ · 01-31-2014, 03:26 AM

Also, is there an easy was to, essentially, "turn on/off" the internet sharing? I'd like to be able to control it easily without deleting/re-adding rules and such.

myatthu · 01-31-2014, 11:19 AM

This guide is specific for debian flavour.

http://chrisjrob.com/2011/03/14/shar...ethernet-port/

In order to automate or run as service, you just need basic script skill and can create custom init script.

PS: Pls thank to original writer for his good guide

slacker_ · 01-31-2014, 02:37 PM

Quote:

Originally Posted by myatthu

This guide is specific for debian flavour.

http://chrisjrob.com/2011/03/14/shar...ethernet-port/

In order to automate or run as service, you just need basic script skill and can create custom init script.

PS: Pls thank to original writer for his good guide

Brilliant, thanks for the alternate guide.

As far as the init script, I'm not 100% sure what that script would need to do. I'm guessing the following:

Code:

[when first run]
test if the following is already in place{
bring the eth connection down, set to static ip
set the rules for iptables
uncomment the lines in /etc/dnsmasq.conf
}
[then when run again]

test if the above is running, and if so complete the following{
comment out the lines in /etc/dnsmasq.conf
remove/hide/disable the rules for iptables
bring eth down, reset to take dynamic ip
}

Is that right, or am I thinking about it incorrectly? I've never written a script like this, and an init script seems all the more complicated if I want to bring the sharing service up/down at will.

myatthu · 01-31-2014, 06:56 PM

You can take a look /etc/rc.d/init.d directory for build in scripts for other services.
You can put your requirements accordingly.