To share 3g internet connection over Ethernet first connect the usb device and activate it.I did it using pppconfig as explained here
Then install firestarter software
sudo apt-get install firestarter
Connect the ethernet cable between two systems,turn off wifi and make sure you have internet access.
Select network connection add a new wired connection,i gave the name as “shared” to identify easily
Edit the wired connections IPV4 Setting
change from dhcp to manual and enter the following details
address = 192.168.13.1 netmask = 255.255.255.0 leave gateway blank
alright now start firestarter
go to “applications” “internet” “firestarter”
use the wizard and select ppp0 as your internet device
select connection sharing and
then use eth0 as your sharing device
dhcp will be greyed out its ok no problem.
On Client PC
Plug the open end of ethernet cable to another system
start firestarter firewall ,now configure another computer to use this gateway
set your ip address to be 192.168.13.15 netmask 255.255.255.0 router (or default gateway) 192.168.13.1
In DNS section you can use opendns ip’s 126.96.36.199 , 188.8.131.52
Now just try pinging.
Happy Hacking 🙂