Wireless ICS network without a router

andou · 02-05-2010, 01:12 PM

I have a desktop running Ubuntu 9.10 with a D-Link WUA-1340 (Supported - last on list) USB wireless adapter, through which I would like to set up a wireless network for internet connection sharing at home.

I have 2 ethernet adapters on my desktop (Eth0, Eth1), and an Apple Airport Express, which I initially tried to use, then thought it might be better to just bypass the Airport Express.

I have worked through a couple tutorials for this on the Ubuntu forums:

InternetConnectionSharing
WifiDocsShareEthernetConnectionThroughWireless
WifiDocsAdhoc

My problem is that although I create a wireless network and connect to it with my macbook, I am unable to access the Internet on it.

Any troubleshooting advice would be appreciated. I am not sure what I am doing wrong, and have worked through WifiDocsShareEthernetConnectionThroughWireless a few times, as this seems to be exactly what I am trying to do.

I am quite new to networking, so any other reference points that you feel may be beneficial would also be appreciated. Thank you.

hunternet93 · 02-06-2010, 10:28 PM

You need to set up IP Masquerading. Here's a script I've used to share an internet connection:

Code:

# Defines the location of iptables executables.
iptables=/sbin/iptables

#Clears if any old iptable rules/ policies are there.
iptables --flush -t nat

 # Now we will do Masquerading ie. we are doing NAT.
iptables --table nat --append POSTROUTING --out-interface wlan0 -j MASQUERADE
iptables --append FORWARD --in-interface usb0 -j ACCEPT

 # Enabling packet forwarding.
echo 1 > /proc/sys/net/ipv4/ip_forward

Save this in a file, and change wlan0 to whatever your interface with an internet connection is (probably eth0), and usb0 to your wireless card's interface (probably wlan0). I hope this works!

andou · 02-07-2010, 06:53 PM

Thanks for the reply.

Do I have to set up Masquerading in order to internet share though?

I've found this How To for Masquerading or IP MASQ, but it's a lot to read and learn simply to set up an Internet sharing network. I am not too worried about security, and I don't think I would need my laptop to access the Internet invisibly, as the text seems to suggest this does.

Also, just wondering where I would save that file, and what I would save it as, or if it matters.

Edit: OK, I managed to get it working. Not sure if this is the best way, but it works for now.

What I did was reworked through InternetConnectionSharing and whereas this was a tutorial for sharing Internet connection eth1 through eth0, I simply replaced eth0 with wlan1 (my wireless network adapter) in:

Code:

sudo iptables -A FORWARD -i eth0 -o eth1 -s 192.168.0.0/24 -m conntrack --ctstate NEW -j ACCEPT
sudo iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
sudo iptables -A POSTROUTING -t nat -j MASQUERADE

and later

Code:

sudo ifconfig eth0 192.168.0.100

Simply by changing those two lines, and setting the Method in IPv4 settings to "Shared to other computers" for the wireless connection I set up on my desktop, I am able to share my Internet connection wirelessly at home.