[CentOS] Network configuration question

Sun Feb 17 17:34:13 UTC 2008
Barry Brimer <lists at brimer.org>

>> I have an older laptop here, a Fujitsu Siemens Amilo D, that I'd like to
>> use as a simple build box. It's physically installed next to my desktop
>> PC. It doesn't have a wireless card, so I vaguely thought: is it somehow
>> possible to connect this laptop with an Ethernet cable to my desktop
>> PC's unused Ethernet card, and then connect it to the internet? In that
>> case, I wonder if I have to bridge the desktop PC's network interfaces
>> (wlan0 and eth0). That said, I don't even know if the driver for wlan0
>> (rt61) allows any bridging. Or maybe simply configure a different
>> subnet, but then, what would the network configuration look like on the
>> laptop and on the desktop PC?
>>
>> Any suggestions for that?

I have not done bridging on CentOS .. but if you want to route to your 
laptop you can do the following:

1.  Enable IP forwarding by changing "net.ipv4.ip_forward = 0" to 
"net.ipv4.ip_forward = 1" in /etc/sysctl.conf and running "sysctl -p".

2.  Put an IP address in an unused private network on the routing 
machine's ethernet card.

3.  If you want to have a separate routed network, you will need to add a 
static route on your internet router that sends traffic to the wireless 
card on your existing network for the wired network segment.  If you want 
to have a network that is masqueraded behind this machine, you do not need 
the static route, but you will need to add a an iptables rule that says 
"iptables -t nat -A POSTROUTING -s <private network behind ethernet card> 
-j MASQUERADE" .. and then run service iptables save to save the changes. 
This is similar to what you would do if you were setting up a Linux 
machine to handle your internet connection.

4.  You will need to statically configure your laptop client on this 
private network to use the ethernet card of your routing machine as its 
default gateway or set up DHCP which instucts it to do the same.

Barry