It's similar to bsc#1105573, after upgrade kernel from v4.17 to v4.18 then the netwok interface fail. But I'm not sure what's the version of your realtek chip. Could you please provide the full 'dmesg' kernel log? Thanks! If your realtek chip is "RTL8169/RTL8169s/RTL8110s", it's worth to try the kmp: https://download.opensuse.org/repositories/home:/david_chang:/bsc1105573/openSUSE_Tumbleweed/x86_64/r8169-kmp-12d42c5-kmp-default-2.3_k4.18.5_1-1.1.x86_64.rpm