For those that need to set a fixed IP on their machine, like me, this is very annoying, so instead of totally removing the network manager, which is what I did last time when I've got mad at it, I've found a better solution I want to share here with you.
If you don't have a DHCP Server, you might have the icon with a red x saying "no network connection"
In either case, right click on the Network Manager icon and chose "Edit Connections"
You'll see this window
Select the Auto eth0 and click "Edit"
When you get here, select and copy the MAC Address
Click "Cancel" and go back to the Network Connections Window and click "Add"
On the Connection Name you can put any name you want, I named it "Manual eth0" and on the MAC Address you need to paste the one you've copied before from Auto eth0, this is the hardware address of the network card you will use for this connection, in this case I have only one so it's simple.
Now go to the "IPv4 Settings" tab and select Method "Manual"
In the "Addresses" section click "Add" and type your desired IP, Netmask and default gateway. Double click on every field, enter the settings and end with Enter. You'll need to set DNS servers manually too, in order to be able to surf the web, if you're behind a router, setting the same IP as the default gateway would be your best bet. If you have more than one DNS server separate them by a comma.
Click "OK" and close the Network Connections window, you'll see the network manager will try to reconnect again, but it won't be able to do it automatically if you don't use a DHCP server, so in order to use the recently created "Manual" connection, click on the Network Manager icon and select the "Manual eth0"
That's it, you're set, now you have your fixed desired settings that will remain set even after reboot.
Hope this helps
