Comment 102 for bug 1752772

$ uname -r
4.15.0-33-generic

$ sudo lshw -C network

  *-network
       Beschreibung: Ethernet interface
       Produkt: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
       Hersteller: Realtek Semiconductor Co., Ltd.
       Physische ID: 0
       Bus-Informationen: pci@0000:02:00.0
       Logischer Name: enp2s0
       Version: 03
       Seriennummer: e0:cb:4e:eb:9e:54
       Größe: 1Gbit/s
       Kapazität: 1Gbit/s
       Breite: 64 bits
       Takt: 33MHz
       Fähigkeiten: pm msi pciexpress msix vpd bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       Konfiguration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl_nic/rtl8168d-2.fw ip=192.168.2.50 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s
       Ressourcen: irq:18 ioport:e800(Größe=256) memory:fafff000-faffffff memory:faff8000-faffbfff memory:fbef0000-fbefffff

LAN disappears when wake up from hibernation.
Script in /lib/systemd/system-sleep/ with

#!/bin/bash
PROGNAME=$(basename "$0")
state=$1
action=$2

if [[ $state == post ]]; then
    modprobe -r r8169 \
    && modprobe -i r8169 \
fi

seems to be a workaround (tested twice).

greetings
andreas