Solution 1
Step 1 – Remove the Gnome Network Manager: You need to complete this step first because if left installed this application will overwrite any changes you make to your configuration when the system is rebooted. This is apparently where the bug is located.
To remove the Gnome Network Manager issue the following command in the terminal:
sudo update-rc.d -f NetworkManager remove
This will disable and remove the Gnome Network Manager application. Now you will have to edit your configuration manually.
Restart your System
Step 2 – Manual configuration of your network interface: In this step you will manually configure your network interface by editing the following two files using your preferred text editor(nano gedit vi). For the purpose of this example I am using the nano editor.
Step 2.1 – Manually configure your network interface file: You can edit the appropriate file by entering the following command into the terminal:
sudo nano /etc/network/interfaces
Once your prefered editor opens the file you want to enter the following information (changing your addresses where necessary):
auto lo eth0
iface lo inet loopback
iface eth0 inet static
address xxx.xxx.xxx.xxx(enter your ip here)
netmask xxx.xxx.xxx.xxx
gateway xxx.xxx.xxx.xxx(enter gateway ip here)
iface lo inet loopback
iface eth0 inet static
address xxx.xxx.xxx.xxx(enter your ip here)
netmask xxx.xxx.xxx.xxx
gateway xxx.xxx.xxx.xxx(enter gateway ip here)
Step 2.2 – Manually configure your dns configuration file: You can edit the appropriate file by entering the following command into the terminal:
sudo nano /etc/resolv.conf
Once your preferred editor opens the file you want to enter the following information (changing your addresses where necessary):
# Generated by NetworkManager
nameserver xxx.xxx.xxx.xxx(enter your dns server ip)
nameserver xxx.xxx.xxx.xxx(enter your alt dns server ip)
nameserver xxx.xxx.xxx.xxx(enter your dns server ip)
nameserver xxx.xxx.xxx.xxx(enter your alt dns server ip)
Step 2.3 – Manually restart your network interface with the new settings: Enter the following command in the terminal:
sudo /etc/init.d/networking restart
This should return a result that looks like the following:
*Reconfiguring network interfaces… [OK]
At this point in your terminal you should be able to run the ifconfig command and the results should reflect your new settings. If the addressing is correct you should have full network access, even after a system restart.
Haven’t tried reinstalling the Network Manger after doing these steps to see if it still works.
Solution 2
Install Wicd if you need both wired and wireless connection
Solution 3
Also, it is said that adding a new config in networkmanager (instead of editing the system default ‘Auto eth0′ stuff) and assign the right MAC address (and the static ip) will fix it, every thing’s fine even after reboot, and you can still use that gnome-networkmanager.
Check this simple guide
Credit Goes here