this is largely a repost of this archlinux topic

I'm connected to my router both with wireless adapter and by wire. Recently the ethernet interface started failing with what looked like DNS issues (resolving host... into ERR_ADDRESS_UNREACHABLE), though everything would become unreachable, even the router's web interface page (which is accessed with plain IP). Disconnecting the interface so that wireless kicks in removes the problem. For a few minutes after that the interface fails to get address from router (apparently the unsuccessfull attempts don't even appear in router's log), but when DHCPREQUEST finally goes through, everything goes back to 'normal'.

I use NetworkManager on top of wpa_supplicant, Arch Linux x86-64, plasma 5.9.2.

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ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 74:d4:35:ae:3e:9d brd ff:ff:ff:ff:ff:ff
3: wlp6s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DORMANT group default qlen 1000
    link/ether e8:94:f6:a6:33:c6 brd ff:ff:ff:ff:ff:ff

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dmesg | grep eth
[    2.441161] r8169 0000:03:00.0 eth0: RTL8168evl/8111evl at 0xffffc9000199d000, 74:d4:35:ae:3e:9d, XID 0c900800 IRQ 36
[    2.441162] r8169 0000:03:00.0 eth0: jumbo features [frames: 9200 bytes, tx checksumming: ko]
[    2.503286] r8169 0000:03:00.0 enp3s0: renamed from eth0


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03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)
        Subsystem: Gigabyte Technology Co., Ltd Onboard Ethernet
        Flags: bus master, fast devsel, latency 0, IRQ 36
        I/O ports at d000 [size=256]
        Memory at f7900000 (64-bit, non-prefetchable) [size=4K]
        Memory at ea100000 (64-bit, prefetchable) [size=16K]
        Capabilities: <access denied>
        Kernel driver in use: r8169
        Kernel modules: r8169


journal output at the moment of issue doesnt really give any clues: lots of QXcbConnection errors which i think are related to missing oxygen or something.

At least 1 more person experiences same issues using Plasma but with different card so a driver issue is unlikely though possible.

Thanks in advance.