Arch Linux

Nietchev

Member

Registered: 2025-06-06

Posts: 5

Erratic Behavior of Lan connection

Hi !

Recently got a fresh install of arch on my new laptop and I encounter a weird issue :
My LAN connection is Very Erratic when I reboot my PC:
- I keep bouncing from Up to Down
- I try some things restarting it / verifying that I don't have any competing service... nothing seems to work
- And some time it just works and for hours I can have a stable connection without issue and I have no idea why...

I use NetworkManager and disabled systemd-networkd to avoid conflict

Here is a bit of context:

nmcli

 
enp10s0: connected to Freebox Lan
        "Realtek RTL8125 2.5GbE"
        ethernet (r8169), 10:FF:E0:B3:0D:BA, hw, mtu 1500
        ip4 default
        inet4 192.168.1.64/24
        route4 192.168.1.0/24 metric 100
        route4 default via 192.168.1.254 metric 100
        inet6 fe80::e9a2:9fd3:7ee9:3e02/64
        route6 fe80::/64 metric 1024

lo: connected (externally) to lo
        "lo"
        loopback (unknown), 00:00:00:00:00:00, sw, mtu 65536
        inet4 127.0.0.1/8
        inet6 ::1/128

wlan0: unavailable
        "Realtek RTL8922AE 802.11be"
        wifi (rtw89_8922ae), 4E:F3:19:08:FD:72, sw disabled, hw, mtu 1500

DNS configuration:
        servers: 192.168.1.254
        interface: enp10s0

Ip link

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp10s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 10:ff:e0:b3:0d:ba brd ff:ff:ff:ff:ff:ff
    altname enx10ffe0b30dba
4: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DORMANT group default qlen 1000
    link/ether 4e:f3:19:08:fd:72 brd ff:ff:ff:ff:ff:ff permaddr 58:10:31:eb:d7:54

find /etc/systemd -type l -exec test -f {} \; -print | awk -F'/' '{ printf ("%-40s | %s\n", $(NF-0), $(NF-1)) }' | sort -f

bluetooth.service                        | bluetooth.target.wants
dbus-org.bluez.service                   | system
dbus-org.freedesktop.nm-dispatcher.service | system
dbus-org.freedesktop.resolve1.service    | system
dbus-org.freedesktop.timesync1.service   | system
fstrim.timer                             | timers.target.wants
getty@tty1.service                       | getty.target.wants
iwd.service                              | multi-user.target.wants
NetworkManager.service                   | multi-user.target.wants
NetworkManager-wait-online.service       | network-online.target.wants
p11-kit-server.socket                    | sockets.target.wants
pipewire-pulse.socket                    | sockets.target.wants
pipewire-session-manager.service         | user
pipewire.socket                          | sockets.target.wants
remote-fs.target                         | multi-user.target.wants
systemd-resolved.service                 | sysinit.target.wants
systemd-timesyncd.service                | sysinit.target.wants
systemd-userdbd.socket                   | sockets.target.wants
wireplumber.service                      | pipewire.service.wants
xdg-user-dirs-update.service             | default.target.wants

And when I do :
sudo dmesg | grep r8169

[ 1055.858285] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1058.607737] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1061.441673] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1064.336988] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1067.172819] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1069.980232] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1072.815687] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1077.070477] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1079.915592] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1083.319797] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1086.155045] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1088.954662] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1091.803628] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1094.826501] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1097.663649] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1102.038383] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1104.868162] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1107.545326] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1110.379626] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1113.954020] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1116.806248] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1119.758759] r8169 0000:0a:00.0 enp10s0: Link is Down

It keeps bouncing like that with me having like a few seconds of internet

Last edited by Nietchev (Yesterday 07:36:41)

seth

Member

Registered: 2012-09-03

Posts: 64,233

Re: Erratic Behavior of Lan connection

Please use [code][/code] tags, not "quote" tags. Edit your post in this regard.
Disable iwd.service, if you want to use iwd as NM backend, see https://wiki.archlinux.org/title/Networ … Fi_backend

Also please post the output of

find /etc/systemd -type l -exec test -f {} \; -print | awk -F'/' '{ printf ("%-40s | %s\n", $(NF-0), $(NF-1)) }' | sort -f

(We figured at some point that systemctl doesn't list all services and the critical one at the time was a dhcpcd one…)

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Nietchev

Member

Registered: 2025-06-06

Posts: 5

Re: Erratic Behavior of Lan connection

updated the post

seth

Member

Registered: 2012-09-03

Posts: 64,233

Re: Erratic Behavior of Lan connection

Disable iwd.service, if you want to use iwd as NM backend, see https://wiki.archlinux.org/title/Networ … Fi_backend

If that doesn't fix it, please post your complete system journal for the boot:

sudo journalctl -b | curl -F 'file=@-' 0x0.st

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Nietchev

Member

Registered: 2025-06-06

Posts: 5

Re: Erratic Behavior of Lan connection

Hey Thanks a lot it seems to be better now.

If you have 1 minute, Just for me to understand :

I made sure to check for conflicting Network manager with :

systemctl --type=service | grep running

and Iwd was not running....

Why can a service hide like that ? and what exactly is the command line you shared outputting and why is it different from the systemctl list ?

Nietchev

Member

Registered: 2025-06-06

Posts: 5

Re: Erratic Behavior of Lan connection

hum actually it seems to solve one issue but I still get a weird behavior:

dmesg | grep r8169

[ 1345.502255] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1348.349216] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1351.179483] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1353.975675] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1356.799865] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1359.748940] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1362.576728] r8169 0000:0a:00.0 enp10s0: Link is Up - 2.5Gbps/Full - flow control off
[ 1365.329254] r8169 0000:0a:00.0 enp10s0: Link is Down
[ 1367.670305] r8169 0000:0a:00.0 enp10s0: Link is Up - 1Gbps/Full - flow control off

And then no update and running smooth.

It seems it erratic when trying the 2.5 gbps interface and after some time bouncing it settle on the 1G speed and is happy....
Can i force the speed to go for 1g by default then with something like ?

ethtool -s enp10s0 speed 1000 

seth

Member

Registered: 2012-09-03

Posts: 64,233

Re: Erratic Behavior of Lan connection

iwd.service was in the original postm why I pointed it out in my first reponse.

So cable problem?
https://wiki.archlinux.org/title/Networ … link_speed

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Nietchev

Member

Registered: 2025-06-06

Posts: 5

Re: Erratic Behavior of Lan connection

Its look like it I just bought a new cable certified for higher speed. I keep you updated on the results.

@Seth : Thanks for the Help I think having 2 issues in parallel got me lost