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#1 2023-01-31 14:36:38

moutan
Member
Registered: 2023-01-20
Posts: 2

Sudden Unreliable Connectivity in local network. NetworkManager

This is the first time I am resorting to posting on forums as I can not fix my issue after more than a week of looking for solutions. Please bear with me as I am quite new to networking concepts in general.

I have a dual boot setup with Windows. I am connected to a local network with a wired connection. On Windows, internet  access works without problems. However, since the beginning of January, without any having updated anything in the system, internet access on Linux stopped working reliably. I used NetworkManager to manage networking and have done nothing to configure it beyond what it has done automatically. Also, internet connection over this wired connection has worked reliably for more than 1 year previously.
My issue is the following: The internet access will function for perhaps a few minutes at boot until ceasing to do so. On occasions it might work for longer (maybe a few hours) until the same issue takes place.  I can bring the network interface down and restart it or restart NetworkManager to obtain the same result: a short time of connectivity followed by it not working.

After checking systemd's logs I identified systemd-resolved as the possible culprit:

systemd-resolved: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server 10.16.
systemd-resolved: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server 10.48.
 systemd-resolved: Using degraded feature set TCP instead of UDP for DNS server 10.48.16.
 systemd-resolved: Using degraded feature set TCP instead of UDP for DNS server 10.16.24.

Followed sometimes by:

systemd-resolved Failed to send hostname reply: Transport endpoint is not connected

This is invariably the pattern I see once I can not access the internet.

These are the local network's DNS servers. Given that the problem seemed to be at least partly related to DNS, I have tried setting the DNS servers to a public one. And indeed, this does seem to fix the problem partly. By changing the DNS server to 1.1.1.1 and restarting my wired connection interface, I am able to access the internet much more consistently. However, it has happened that the problem resurfaces even with this new public DNS server set. Here I can simply restart the interface again and thus regain internet access. However, I do not consider this a solution and have had times where the same happened with the public server.

I do not manage the local network and so had thought  that perhaps it had some sort of change to it that only affects Linux systems but there are other Linux machines on the network which were not affected. Also, this is not a distro specific things as I tried fedora, Ubuntu (the one the other Linux machines in the network use) and arch and encountered the same on all of them. 
 
I have also found many posts about people experiencing similar issues in recent months and there never seems to be a definitive unique solution. If someone has some idea of what can be happening I would really appreciate the help. What perplexes me about the issue is that it seems intermittent. I have just had 1 week without anything taking place and using the DNS servers of the network without an issue but it has just resurfaced after a reboot.

Last edited by moutan (2023-02-01 09:15:55)

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#2 2023-01-31 16:49:38

seth
Member
Registered: 2012-09-03
Posts: 52,545

Re: Sudden Unreliable Connectivity in local network. NetworkManager

I have a dual boot setup with Windows

3rd link below. Disable it (it's NOT the BIOS setting!) and reboot windows and linux twice for voodo reasons.

The internet access will function for perhaps a few minutes at boot until ceasing to do so. On occasions it might work for longer (maybe a few hours) until the same issue takes place.  I can bring the network interface down and restart it or restart NetworkManager to obtain the same result: a short time of connectivity followed by it not working.

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

Given that the problem seemed to be at least partly related to DNS

When the connection fails, can yo still

ping -c1 1.1.1.1

?

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#3 2023-02-01 09:14:57

moutan
Member
Registered: 2023-01-20
Posts: 2

Re: Sudden Unreliable Connectivity in local network. NetworkManager

Hey, thanks for the reply.

I have already disabled fast-start when I was looking for solutions. Will try the rebooting voodo, maybe that is what made it work  smile
Actually I do not know if this might be related but things had been working for a few days with me rebooting between OS'es. The problem actually resurfaced when I went into the BIOS to make a change and booted back into Linux.

When the connection fails, (as of right now, I have the the DNS servers set to the internal ones), I can still ping 1.1.1.1 or 8.8.8.8. I however can not ping the DNS server I am supposedly using (10.48.16.7). I  also can not ping any other internal machines in the network, even with their IP. Here is the output of "resolvectl status" for my wired interface in case it helps.

Link 2 (eno1)
    Current Scopes: DNS LLMNR/IPv4
         Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=allow-downgrade/unsupported
Current DNS Server: 10.48.16.7
       DNS Servers: 10.16.24.8 10.16.24.7 10.48.16.7

Also, I can not ping something like google.com or youtube.com. However if I go on the browser (I can access the internet  with Firefox by enabling  the DNS over HTTPS setting using CloudFlare which I guess bypasses the internal DNS server) and check the IP of some server from a webpage, I can ping it directly with its IP. So again, it seems it really is just a DNS problem with the internal servers. As soon as I switch to the use the public DNS server (1.1.1.1) I am able to ping public domain names.

Here is the output of the command you asked:

abrt-journal-core.service                | multi-user.target.wants
abrt-oops.service                        | multi-user.target.wants
abrt-vmcore.service                      | multi-user.target.wants
abrt-xorg.service                        | multi-user.target.wants
abrtd.service                            | multi-user.target.wants
accounts-daemon.service                  | graphical.target.wants
akmods.service                           | multi-user.target.wants
auditd.service                           | multi-user.target.wants
avahi-daemon.service                     | multi-user.target.wants
avahi-daemon.socket                      | sockets.target.wants
bluetooth.service                        | bluetooth.target.wants
chronyd.service                          | multi-user.target.wants
ctrl-alt-del.target                      | system
cups.path                                | multi-user.target.wants
cups.socket                              | sockets.target.wants
dbus-org.bluez.obex.service              | user
dbus-org.bluez.service                   | system
dbus-org.freedesktop.Avahi.service       | system
dbus-org.freedesktop.home1.service       | system
dbus-org.freedesktop.ModemManager1.service | system
dbus-org.freedesktop.nm-dispatcher.service | system
dbus-org.freedesktop.oom1.service        | system
dbus-org.freedesktop.resolve1.service    | system
dbus-org.freedesktop.thermald.service    | system
dbus.service                             | system
dbus.service                             | user
dbus.socket                              | sockets.target.wants
dbus.socket                              | sockets.target.wants
default.target                           | system
display-manager.service                  | system
dm-event.socket                          | sockets.target.wants
firewalld.service                        | multi-user.target.wants
fstrim.timer                             | timers.target.wants
getty@tty1.service                       | getty.target.wants
import-state.service                     | sysinit.target.wants
iscsi-onboot.service                     | sysinit.target.wants
iscsi.service                            | remote-fs.target.wants
iscsid.socket                            | sockets.target.wants
iscsiuio.socket                          | sockets.target.wants
lm_sensors.service                       | multi-user.target.wants
logrotate.timer                          | timers.target.wants
low-memory-monitor.service               | basic.target.wants
lvm2-lvmpolld.socket                     | sysinit.target.wants
lvm2-monitor.service                     | sysinit.target.wants
mcelog.service                           | multi-user.target.wants
mdmonitor.service                        | multi-user.target.wants
mlocate-updatedb.timer                   | timers.target.wants
ModemManager.service                     | multi-user.target.wants
multipathd.service                       | sysinit.target.wants
multipathd.socket                        | sockets.target.wants
NetworkManager-wait-online.service       | network-online.target.wants
NetworkManager.service                   | multi-user.target.wants
nfs-client.target                        | multi-user.target.wants
nfs-client.target                        | remote-fs.target.wants
nfs-convert.service                      | nfs-blkmap.service.requires
nfs-convert.service                      | nfs-idmapd.service.requires
nfs-convert.service                      | nfs-mountd.service.requires
nfs-convert.service                      | nfs-server.service.requires
nfs-convert.service                      | rpc-gssd.service.requires
nfs-convert.service                      | rpc-statd-notify.service.requires
nfs-convert.service                      | rpc-statd.service.requires
nv-power-limit.service                   | multi-user.target.wants
nv-power-limit.service                   | system
nvidia-hibernate.service                 | systemd-hibernate.service.wants
nvidia-powerd.service                    | multi-user.target.wants
nvidia-resume.service                    | systemd-hibernate.service.wants
nvidia-resume.service                    | systemd-suspend.service.wants
nvidia-suspend.service                   | systemd-suspend.service.wants
ostree-remount.service                   | local-fs.target.wants
pcscd.socket                             | sockets.target.wants
pipewire-pulse.socket                    | sockets.target.wants
pipewire-session-manager.service         | user
pipewire.socket                          | sockets.target.wants
power-profiles-daemon.service            | graphical.target.wants
qemu-guest-agent.service                 | dev-virtio\x2dports-org.qemu.guest_agent.0.device.wants
raid-check.timer                         | timers.target.wants
remote-fs.target                         | multi-user.target.wants
rtkit-daemon.service                     | graphical.target.wants
selinux-autorelabel-mark.service         | sysinit.target.wants
sssd-kcm.socket                          | sockets.target.wants
sssd.service                             | multi-user.target.wants
switcheroo-control.service               | graphical.target.wants
systemd-homed-activate.service           | systemd-homed.service.wants
systemd-homed.service                    | multi-user.target.wants
systemd-oomd.service                     | multi-user.target.wants
systemd-resolved.service                 | multi-user.target.wants
systemd-tmpfiles-clean.timer             | timers.target.wants
systemd-tmpfiles-setup.service           | basic.target.wants
systemd-userdbd.socket                   | sockets.target.wants
thermald.service                         | multi-user.target.wants
udisks2.service                          | graphical.target.wants
unbound-anchor.timer                     | timers.target.wants
upower.service                           | graphical.target.wants
uresourced.service                       | user@.service.wants
vboxservice.service                      | multi-user.target.wants
vgauthd.service                          | vmtoolsd.service.requires
virtinterfaced.socket                    | sockets.target.wants
virtlockd.socket                         | sockets.target.wants
virtlogd.socket                          | sockets.target.wants
virtnetworkd.socket                      | sockets.target.wants
virtnodedevd.socket                      | sockets.target.wants
virtnwfilterd.socket                     | sockets.target.wants
virtproxyd.socket                        | sockets.target.wants
virtqemud-admin.socket                   | sockets.target.wants
virtqemud-ro.socket                      | sockets.target.wants
virtqemud.service                        | multi-user.target.wants
virtqemud.socket                         | sockets.target.wants
virtsecretd.socket                       | sockets.target.wants
virtstoraged.socket                      | sockets.target.wants
vmtoolsd.service                         | multi-user.target.wants
wireplumber.service                      | pipewire.service.wants

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#4 2023-02-01 11:30:22

seth
Member
Registered: 2012-09-03
Posts: 52,545

Re: Sudden Unreliable Connectivity in local network. NetworkManager

What does "unbound-anchor.timer" and does its action correlate w/ the DNS losses?

10.48.16.7 is a private address (like 192.168.0.7) - what's the output of

ip a; ip r

Also the "| system" and "| user" entries look fishy.

stat /etc/systemd/system/dbus.service

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