Another Windows migrant here. I can’t get my ethernet to work but wifi works OK. I am almost certain that when I installed Debian Trixie with KDE Plasma a few weeks ago, ethernet worked but it stopped a day or so later. Info Centre reports:

2: enp0s25: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
link/ether 54:ee:75:52:01:23 brd ff:ff:ff:ff:ff:ff
altname enx54ee75520123
3: enx0050b6c0f7f3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:50:b6:c0:f7:f3 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.92/24 brd 192.168.1.255 scope global dynamic noprefixroute enx0050b6c0f7f3
valid_lft 3419sec preferred_lft 2969sec
inet6 fe80::8437:d694:3204:62ff/64 scope link
valid_lft forever preferred_lft forever

I deleted the wired connection in System Settings | Wi-Fi & Networking and it was recreated which probably suggests the ethernet connection is detected even if the fields there are all blank. Also, the internet traffic plasmoid shows enx0050b6c0f7f3 with around 1/5 of the cumulative traffic of wifi.

I tried the obvious things, just in case. I disabled the firewall, restarted the router, deleted the wired connection, played with settings in Wi-Fi & Networking and tried dhcpcd.

$ sudo dhcpcd 
main: control_open: Connection refused 
dhcpcd-10.1.0 starting 
dev: loaded udev 
DUID 00:01:00:01:30:54:2e:d5:00:50:b6:c0:f7:f3 
wlp4s0: connected to Access Point: glocal 
enp0s25: waiting for carrier 
enx0050b6c0f7f3: IAID b6:c0:f7:f3 
wlp4s0: IAID 86:9b:42:5e 
enx0050b6c0f7f3: soliciting an IPv6 router 
wlp4s0: soliciting an IPv6 router 
wlp4s0: rebinding lease of 192.168.1.122 
wlp4s0: probing address 192.168.1.122/24 
enx0050b6c0f7f3: rebinding lease of 192.168.1.216 
enx0050b6c0f7f3: leased 192.168.1.216 for 3600 seconds 
enx0050b6c0f7f3: adding route to 192.168.1.0/24 
enx0050b6c0f7f3: adding default route via 192.168.1.254

and sudo systemctl status NetworkManager.service returns

●NetworkManager.service - Network Manager
Loaded: loaded (/usr/lib/systemd/system/NetworkManager.service;enabled; preset: enabled) 
Active:active (running)since Sun 2025-10-12 23:59:31 BST; 47min ago
Invocation: a3faea14d3dc48e29a2e2d27750ca082
  Docs: man:NetworkManager(8)
  Main PID: 98676 (NetworkManager)
 Tasks: 4 (limit: 9149)
Memory: 6.3M (peak: 7.1M)
   CPU: 2.457s
CGroup: /system.slice/NetworkManager.service
└─98676 /usr/sbin/NetworkManager --no-daemon

Oct 13 00:03:10 tpkde NetworkManager[98676]: <info>  [1760310190.8454] dhcp4 (wlp4s0): activation: beginning transaction (timeout in 45 seconds) 
Oct 13 00:03:10 tpkde NetworkManager[98676]: <info>  [1760310190.8623] dhcp4 (wlp4s0): state changed new lease, address=192.168.1.85, acd pending 
Oct 13 00:03:11 tpkde NetworkManager[98676]: <info>  [1760310191.0217] dhcp4 (wlp4s0): state changed new lease, address=192.168.1.85 
Oct 13 00:03:11 tpkde NetworkManager[98676]: <info>  [1760310191.0237] policy: set 'glocal' (wlp4s0) as default for IPv4 routing and DNS 
Oct 13 00:03:11 tpkde NetworkManager[98676]: <info>  [1760310191.0440] device (wlp4s0): state change: ip-config -> ip-check (reason 'none', managed-type: 'full') 
Oct 13 00:03:11 tpkde NetworkManager[98676]: <info>  [1760310191.0839] device (wlp4s0): state change: ip-check -> secondaries (reason 'none', managed-type: 'full') 
Oct 13 00:03:11 tpkde NetworkManager[98676]: <info>  [1760310191.0841] device (wlp4s0): state change: secondaries -> activated (reason 'none', managed-type: 'full') 
Oct 13 00:03:11 tpkde NetworkManager[98676]: <info>  [1760310191.0855] device (wlp4s0): Activation: successful, device activated. 
Oct 13 00:03:11 tpkde NetworkManager[98676]: <info>  [1760310191.1033] audit: op="statistics" interface="wlp4s0" ifindex=4 args="2000" pid=1511 uid=1000 result="succe> 
Oct 13 00:33:10 tpkde NetworkManager[98676]: <info>  [1760311990.8671] dhcp4 (wlp4s0): state changed new lease, address=192.168.1.85

Not sure if this is relevant, but DCHP is handled by pi.hole on a Raspberry Pi. This has been working serving multiple devices for a long time without issues. Also, this is temporarily a dual boot Windows/Linux setup. When I log out and into Windows, everything works as ever.

After several days trying, I ran out of ideas. Can someone help please.

EDIT: SOLVED! In case it helps others, reading https://wiki.debian.org/NetworkManager closely, I ran nmcli device which showed that specific ethernet interface as ‘unmanaged’. I am not sure why. Then, I followed the instructions below:

If you want NetworkManager to handle interfaces that are enabled in /etc/network/interfaces:

Set managed=true in a drop-in file in /etc/NetworkManager/NetworkManager.conf.d/ or directly in /etc/NetworkManager/NetworkManager.conf.

Debian documentation could be more accessible, but it is invaluable. Thanks all for your help.

  • Stopwatch1986@lemmy.mlOP
    2·
    14 hours ago

    Good idea. With the live USB my ethernet works fine right from the start. So, it’s not hardware or windows. The one difference I see between the live USB and my current setup is that in the live USB session sudo systemctl status NetworkManager.service returns also the line below which is missing when I execute the command in my actual setup:

    audit: op="statistics" interface="enx0050b6cOf7f3" if index=3 args="2000" pid= 1957 uid=1000 result="success"

    But Info Center in KDE Plasma lists “enx0050b6cOf7f3” as in my original post.

    So, ethernet hardware functions, it works as expected with live USB and Windows. In the debian setup it is detected with an inet address, but NetworkManager ignores it.

    DHCP also works – my wifi connection in this debian setup works, as do several devices connected to wifi and ethernet.