Ubuntu 18.04 new install, no ethernet or wifi

[ubucat2]

Some weeks ago I upgraded the second PC to Ubuntu 18.04, after the installation had worked fine on the first one. This second PC is a Gigabyte F2A88X-D3H with BIOS 08-19-2013, running ubuntu 18.04 - 4.15.0-30-generic ... and has an on-board ethernet RTL8111/8168/8411 PCI .... lsmod |grep 816 --> r8169 - 86016 - 0, mii - 16384 - 1 r8169.
The day before yesterday I could not connect to the Web. I could not even ping the router. I checked everything, but did not find a clue. At last I disabled the onboard ethernet and inserted a PCI-Network-Card. Same RTL-Chip, same driver. Network was now indicated as up, but the symbol on the top-line showed a question mark in the center of the three squares, ping didn't work, and no connection was possible.
After a lot of reading I discovered the tool mii-diag_2.11-3_amd64.deb, which I installed with sudo dpkg ... and ran as sudo mii-diag -v enp1s0. Well, I still can't believe it, but after that the network was suddenly up, and I write this message on this very PC. The previously upgraded PC runs 18.04 - 4.15.0-23 with the same ethernet hardware and drivers.

[ubucat2]

Just updated the Gigabyte F2A88X-D3H to 4.15.0.33 and network is still up. Considering that I had 4.15.0.30 running flawlessly for several weeks before the network out of the blue fell apart, the bug-hunt will be somewhat demanding, because a simple go-nogo-test will not suffice, and it is by no means clear, where the bug sits - in the Realtek chip, in the driver, or in the OS. For me, applying mii-diag was quite satisfying to regain network functionality.

[cjklmnop]

Some weeks ago I upgraded the second PC to Ubuntu 18.04, after the installation had worked fine on the first one. This second PC is a Gigabyte F2A88X-D3H with BIOS 08-19-2013, running ubuntu 18.04 - 4.15.0-30-generic ... and has an on-board ethernet RTL8111/8168/8411 PCI .... lsmod |grep 816 --> r8169 - 86016 - 0, mii - 16384 - 1 r8169.
The day before yesterday I could not connect to the Web. I could not even ping the router. I checked everything, but did not find a clue. At last I disabled the onboard ethernet and inserted a PCI-Network-Card. Same RTL-Chip, same driver. Network was now indicated as up, but the symbol on the top-line showed a question mark in the center of the three squares, ping didn't work, and no connection was possible.
After a lot of reading I discovered the tool mii-diag_2.11-3_amd64.deb, which I installed with sudo dpkg ... and ran as sudo mii-diag -v enp1s0. Well, I still can't believe it, but after that the network was suddenly up, and I write this message on this very PC. The previously upgraded PC runs 18.04 - 4.15.0-23 with the same ethernet hardware and drivers.

Hello, i have the same problem and can not use or see my ethernet port on my laptop despite wifi is working, after reinstalling ubuntu desktop. Can you be a little bit more specific how you solved this problem after installing the mii-diag_2.11-3_amd64.deb? the command sudo mii-diag -v enp1s0 does returns error: SIOCGMIIPHY on enp1s0 failed: No such device .

thank you!