Problem in connecting the Laptop and Desktop's LAN and INTERNET simultaneously

hvpraveen · 02-26-2009, 01:34 PM

Hi,

I am trying to set up simple LAN between my Laptop and Desktop PC. I have connected Laptop to INTERNET via a wireless modem though DHCP. Laptop and Desktops are connected to each other through CAT-5e cable.

So far, I am to connect INTERNET to my Laptop separately without having the connection to the Desktop. And, also I am able to communicate between Laptop and Desktop without having the INTERNET connection to Laptop. But, If I connect Laptop and Desktop and also laptop to internet, I loose the INTERNET connection from my Laptop. I can't have both the connections work simultaneously. I can't access Internet (even from Laptop) as long as Laptop and desktops are connected.

Following are the Laptop's wireless connection details:

Interface: 802.11 WiFi (wlan0)
IP Address: 192.168.1.2
Subnet Mask: 255.255.255.0
Gate way: 192.168.1.1

For Laptop wired ethernet network, I have manually assigned following IPs.

Interface: ethernet (eth0)
IP Address: 192.168.1.3
Subnet Mask: 255.255.255.0
Gate way: 192.168.1.1

For Desktop wired ethernet network, I have manually assigned following IPs.

Interface: ethernet (eth0)
IP Address: 192.168.1.4
Subnet Mask: 255.255.255.0
Gate way: 192.168.1.1

I want to connect to Laptop and Desktop simultaneously while retaining the Internet connection. I would also like to access Internet from the Desktop via Laptop.

Could you folks please help me figure out what problem is in the above setup?

Any help from you folks are greatly appreciated.

Thanks in advance.

Regards,
Praveen

farslayer · 02-26-2009, 02:18 PM

the first problem is that you have both interfaces on the laptop in the same subnet.. you can't route data between interfaces in the same subnet

Laptop
wifi - 192.168.1.2
mask 255.255.255.0
Default gateway 192.168.1.1

eth0
192.168.2.2
mask 255.255.255.0

Desktop
eth0 - 192.168.2.3
mask 255.255.255.0
Default gateway 192.168.2.2

You need to enable ip forwarding in the laptop
http://www.ducea.com/2006/08/01/how-...ding-in-linux/

Then you need to manually add a route in your Wireless access point so that it will know that 192.168.2.0 is through the laptop

Another way would be to install firestarter and check the internet connection sharing box..
http://www.fs-security.com/docs/connection-sharing.php

Either way though you have to correct the addressing on the interfaces in your laptop as I described above.