I have an issue with my rtl8169 gigabit NIC. Which gigabit NICs are supported out of the box by Ubuntu lucid?
Here is the list of network cards that are supported by Ubuntu: Wired Network Cards
The list is broken down by vendor. If you click on a vendor it will take you to a list of that vendors cards that are supported/unsupported.
It seems that your Realtek RTL-8169 is supported, but it doesn't list which version of Ubuntu it is confirmed to work with.