Thank you for contacting the Intel Communities.
I was able to confirm that the Intel® Ethernet Connection I218-V does support (10/100/1000 Mb/s) speeds so that shouldn't be the cause.
Are you seeing these speeds with a speed test from a website? or an specific software being used?
Lets test the network speed using this driver (latest as per 12/14/2015)
Then I would like you to uninstall the driver from the device manager under network adapters and after that, let Windows install the default drivers.
Also, make sure you have the latest drivers for Chipset and Management Engine.
If you are still having issues after the steps above, lets update the BIOS in your system, if already up to date, a recovery would be a good option.