Use ethtool. ethtool can be used to query and change settings such as speed, auto- negotiation and checksum offload on many network devices, especially Ethernet devices.

To install ethtool in ubuntu, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command below.

sudo apt-get install ethtool

If you want to find what type of network card is used, its speed, on which IRQ it is listed, and the chip type used, you use the following command :

dmesg |grep eth0

But keep this in mind:

• Cat 6 cable should squeeze more speed out of your connection


• Cable length - Keep it as short as possible


• Your best speed results will be between 2 computers. Internet usage
  speeds will be lower in most cases.


• Make sure jumbo frames are set in network properties for your network
  adapter.


• Hard Disk speed can bottleneck your transfers