I've got an Intel NUC D34010WYK with XBMC Libreelec installed (latest version) and with latest BIOS. The NUC is connected to the home gigabit Ethernet for streaming 4K videos and music from my main PC. I face to following problem. I recently changed my router (a Dlink 2740 100mbit ethernet) to an ASUS N17U with gigabit ethernet. Every gigabit device in my home network is working now with gigabit speeds normally but the NUC is not. When my PCs LAN adapter is set to Gigabit speed the file transfer speed isn't higher than 2-3MB/S. When I set the LAN adapter in my PC to 100mbit the speed rises to the normal 11mb/s. Playback with "gigabit" speed has issues of course with that low bandwidth. I've done many tests, the PC's LAN controller is OK, router and cables too, even my gigabit switch. I've also tried connecting the NUC directly to the router with gigabit enabled LAN from my PC and still the speed is dramatically low. As it seems there is an issue with the NUC's LAN controller when receiving "gigabit" speed whereas it's quite OK when set to 100mbit. Any ideas or solution to the issue?
Please bear in mind that Intel has not validated this operating system with this Intel® NUC, we recommend check your distro's website and forums for peer assistance. You can see Supported Operating Systems for Intel® NUC Products.
Have you contacted ASUS for latest firmware for your router? Here are some links that might be helpful for you.