Comment # 55 on bug 1188949 from Reinhard Max

Raija, thanks for your efforts! The logs you provided are appreciated.

But your issue seems to have a different reason than Vladislav's, although the
symptoms might look similar at first sight.

Both systems have network cards that are run by the r8169 driver, but in your
case the kernel reports an error and stack trace about the driver when the
network goes down (starting with "NETDEV WATCHDOG: enp2s0 (r8169): transmit
queue 0 timed out"), whereas in Vladislav's case no kernel errors happen, but
DHCP-ACK packets are missing.

I'll have another look at this next week and then maybe open a separate bug
report for your issue.

BTW, r8169 has quite a history of being unstable in various ways, I also had
huge problems with it on a rented server a few years ago where I found no
working solution and ended up using an Intel network card instead. Of course
this doesn't help if the network chip is on-board and the board has no slot for
an add-on network card.