It looks like the issue for this user has been solved, but I recently went through the same problems and thought that it would be helpful if I shared how I fixed it.
- Incredibly slow internet speed. (Capping at maybe 50 kbps)
- Perfectly fine internet speed on the Windows 7 installation I am dual-booting with on the same machine.
- RTL8101E/RTL8102E Ethernet Controller (Network Card)
- Note: This may still work for you if that is not your specific Realtek card.
I tried reconfiguring, disabling IPV6, etc ... didn't worked.
I did some reading and found that the Realtek LAN network driver that ships with ubuntu 12.10 (and lower if I recall correctly) is RTL8169. For whatever reason (I am not an expert) the RTL8169 driver does not work correctly with Ubuntu on some installations.
The first thing I recommend that you do is run the following in the terminal:
That will give you a long list of the hardware and software specifications of your machine. You are looking for some lines that will look something like this:
description: Ethernet Interface
product: [The name of your network card] (Mine is RTL8101E/RTL8102E)
configuration: ... ... driver: r8169
If the driver happens to say r8169, that is most likely the problem. What we are going to do from here is 'dowgrade' the driver to one that is more compatible with ubuntu.
Note: As I said, the specific card I have is the RTL8101. The steps may change slightly if you have a different card.
The driver for the RTL8101 card can be found here.
You can do a simple Google search if that is not the driver you need.
Unpack the downloaded file and extract to some place you can conveniently 'cd' to in the terminal. I chose Desktop.
You should now have a folder on your desktop called 'r8101-1.023.00' or similar.
Open the folder and confirm that there is a file called 'autorun.sh' in the folder. If there is not, you will need to read the README inside of the folder to figure out how to manually install the driver.
Otherwise (if there is an 'autorun.sh' in the folder), open the Terminal. Then change directory to the extracted folder.
Run the following command:
That should backup and remove your current RTL driver and install the newly downloaded driver.
Those are the steps that I took to fix the problem on my machine. Best of luck.