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#1 2025-05-01 04:38:26

cfr
Member
From: Cymru
Registered: 2011-11-27
Posts: 7,167

Repeated temporary failures of domain name resolution

I repeatedly get temporary failures in domain name resolution. I typically notice these in chromium, but 

ping www.example.com

fails. Pinging the wifi hub(?) works in almost all cases. (When it fails, I think it is because I've restarted the network service and haven't let it finish figuring things out.) That is, the following works fine:

ping 192.168.5.1

This is the primary one of three Tenda WiFi cubes providing the WIFI LAN. It is connected to a router from the ISP which has WIFI disabled. This has hugely improved the reliability of the LAN and the signal is strong everywhere in the house and in a chunk of the garden, too.

I tried setting chromium to use one of the secure DNS options (OpenDNS)), hoping to force use of a different resolver, but this does not seem to make any difference.

I'm using netctl to manage network connections. 

  netctl-auto@wlan0.service                                loaded active running   Automatic wireless network connection using netctl profiles
  netctl-ifplugd@eth0.service                              loaded active running   Automatic wired network connection using netctl profiles

NetworkManager is installed but masked:

lrwxrwxrwx 1 root root 9 Hyd   4  2017 /etc/systemd/system/NetworkManager.service -> /dev/null

I also have mdns:

  avahi-daemon.socket                                      loaded active running   Avahi mDNS/DNS-SD Stack Activation Socket

But I'm a bit surprised to see:

  wpa_supplicant.service                                   loaded active running   WPA supplicant

as I expected `netctl` to invoke `wpa-supplicant` as necessary.

$ ps ax | grep wpa
    853 ?        Ss     0:01 wpa_supplicant -q -B -P /run/wpa_supplicant-wlan0.pid -i wlan0 -D nl80211,wext -c/run/netctl/wpa_supplicant-wlan0.conf -W
    857 ?        Ss     0:01 wpa_cli -i wlan0 -p /run/wpa_supplicant -B -a /usr/lib/netctl/auto.action
   2410 ?        Ss     0:00 /usr/bin/wpa_supplicant -u -s -O /run/wpa_supplicant
  22622 pts/14   S+     0:00 /usr/bin/grep --colour=auto wpa

Obviously the first two results are netctl, as expected and the fourth is spurious. But is the third a spin off from netctl? Or should that not be there at all?

$ find /etc/systemd -path "*wpa*"

returns nothing. /etc/wpa_supplicant is empty. /etc/wpa_supplicant.conf contains a snippet for another WIFI network from my most recent unsuccessful attempt to tangle with eduroam.

/etc/systemd/network/ is empty. /etc/systemd/networkd.conf contains (minus the comments)

[Network]
#SpeedMeter=no
#SpeedMeterIntervalSec=10sec
#ManageForeignRoutingPolicyRules=yes
#ManageForeignRoutes=yes
#ManageForeignNextHops=yes
#RouteTable=
#IPv6PrivacyExtensions=no
#UseDomains=no

[IPv6AcceptRA]
#UseDomains=

[DHCPv4]
#DUIDType=vendor
#DUIDRawData=
#UseDomains=

[DHCPv6]
#DUIDType=vendor
#DUIDRawData=
#UseDomains=

[DHCPServer]
#PersistLeases=yes

netctl config for my home wifi network:

Description='Enw'
Interface=wlan0
Connection=wireless
Security=wpa
IP=dhcp
ESSID='Enw'
Key=\"<long hash of key>

where Enw is the network name and the key is a hash of the password.
/etc/hosts

# Static table lookup for hostnames.
# See hosts(5) for details.

#<ip-address>   <hostname.domain.org>   <hostname>
127.0.0.1       localhost.localdomain   localhost FyEnw
::1             localhost.localdomain   localhost FyEnw

# End of file

where FyEnw is the name in /etc/hostname.

/etc/resolvconf.conf

# Configuration for resolvconf(8)
# See resolvconf.conf(5) for details

resolv_conf=/etc/resolv.conf
# If you run a local name server, you should uncomment the below line and
# configure your subscribers configuration files below.
#name_servers=127.0.0.1

/etc/resolv.conf

# Generated by resolvconf
domain tendawifi.com
nameserver 192.168.5.1

I've also tried overwriting this file with a copy of /etc/resolv.conf.bak

nameserver 194.168.4.100
nameserver 194.168.8.100

which are my ISP's name servers.

The hardware I'm using is quite old in laptop terms, but the fact I can ping IP addresses makes me suspect a configuration issue rather than some intermittent hardware failure.

How can I figure out what is wrong? Or what do I need to read to figure out how to figure out what is wrong? Is the wpa_supplicant service related to netctl? If not, how can I figure out what is starting it? I re-read the wiki pages on DNS and network configuration, together with some related topics, but the only troubleshooting tip I've gleaned so far is that it might be good to ping 9.9.9.9 the next time resolution fails.

Full listing of units of types service and socket from systemctl:

$ systemctl list-units -t service,socket
  UNIT                                                     LOAD   ACTIVE SUB       DESCRIPTION
  acpid.service                                            loaded active running   ACPI event daemon
  alsa-restore.service                                     loaded active exited    Save/Restore Sound Card State
  auditd.service                                           loaded active running   Security Audit Logging Service
  avahi-daemon.service                                     loaded active running   Avahi mDNS/DNS-SD Stack
  avahi-dnsconfd.service                                   loaded active running   Avahi DNS Configuration Daemon
  chronyd.service                                          loaded active running   NTP client/server
  clamav-daemon.service                                    loaded active running   Clam AntiVirus userspace daemon
  clamav-freshclam.service                                 loaded active running   ClamAV virus database updater
  colord.service                                           loaded active running   Manage, Install and Generate Color Profiles
  cups.service                                             loaded active running   CUPS Scheduler
  dbus-broker.service                                      loaded active running   D-Bus System Message Bus
  espeakup.service                                         loaded active running   Software speech output for Speakup
  geoclue.service                                          loaded active running   Location Lookup Service
  gpservice.service                                        loaded active running   GlobalProtect openconnect DBus service
  ip6tables.service                                        loaded active exited    IPv6 Packet Filtering Framework
  iptables.service                                         loaded active exited    IPv4 Packet Filtering Framework
  kmod-static-nodes.service                                loaded active exited    Create List of Static Device Nodes
  ldconfig.service                                         loaded active exited    Rebuild Dynamic Linker Cache
  lm_sensors.service                                       loaded active exited    Initialize hardware monitoring sensors
  lvm2-monitor.service                                     loaded active exited    Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progress polling
  netctl-auto@wlan0.service                                loaded active running   Automatic wireless network connection using netctl profiles
  netctl-ifplugd@eth0.service                              loaded active running   Automatic wired network connection using netctl profiles
  polkit.service                                           loaded active running   Authorization Manager
  rtkit-daemon.service                                     loaded active running   RealtimeKit Scheduling Policy Service
  sddm.service                                             loaded active running   Simple Desktop Display Manager
  smartd.service                                           loaded active running   Self Monitoring and Reporting Technology (SMART) Daemon
  systemd-backlight@backlight:intel_backlight.service      loaded active exited    Load/Save Screen Backlight Brightness of backlight:intel_backlight
  systemd-fsck@dev-mapper-vgcfr\x2darch\x2d\x2dvar.service loaded active exited    File System Check on /dev/mapper/vgcfr-arch--var
  systemd-fsck@dev-mapper-vgcfr\x2dbetween.service         loaded active exited    File System Check on /dev/mapper/vgcfr-between
  systemd-fsck@dev-mapper-vgcfr\x2dcartref.service         loaded active exited    File System Check on /dev/mapper/vgcfr-cartref
  systemd-fsck@dev-mapper-vgcfr\x2dlleol.service           loaded active exited    File System Check on /dev/mapper/vgcfr-lleol
  systemd-fsck@dev-nvme0n1p1.service                       loaded active exited    File System Check on /dev/nvme0n1p1
  systemd-hwdb-update.service                              loaded active exited    Rebuild Hardware Database
  systemd-journal-catalog-update.service                   loaded active exited    Rebuild Journal Catalog
  systemd-journal-flush.service                            loaded active exited    Flush Journal to Persistent Storage
  systemd-journald.service                                 loaded active running   Journal Service
  systemd-logind.service                                   loaded active running   User Login Management
  systemd-modules-load.service                             loaded active exited    Load Kernel Modules
  systemd-random-seed.service                              loaded active exited    Load/Save OS Random Seed
  systemd-remount-fs.service                               loaded active exited    Remount Root and Kernel File Systems
  systemd-sysctl.service                                   loaded active exited    Apply Kernel Variables
  systemd-sysusers.service                                 loaded active exited    Create System Users
  systemd-tmpfiles-setup-dev-early.service                 loaded active exited    Create Static Device Nodes in /dev gracefully
  systemd-tmpfiles-setup-dev.service                       loaded active exited    Create Static Device Nodes in /dev
  systemd-tmpfiles-setup.service                           loaded active exited    Create System Files and Directories
  systemd-udev-load-credentials.service                    loaded active exited    Load udev Rules from Credentials
  systemd-udev-settle.service                              loaded active exited    Wait for udev To Complete Device Initialization
  systemd-udev-trigger.service                             loaded active exited    Coldplug All udev Devices
  systemd-udevd.service                                    loaded active running   Rule-based Manager for Device Events and Files
  systemd-update-done.service                              loaded active exited    Update is Completed
  systemd-update-utmp.service                              loaded active exited    Record System Boot/Shutdown in UTMP
  systemd-user-sessions.service                            loaded active exited    Permit User Sessions
  systemd-vconsole-setup.service                           loaded active exited    Virtual Console Setup
  thermald.service                                         loaded active running   Thermal Daemon Service
  tlp.service                                              loaded active exited    TLP system startup/shutdown
  udisks2.service                                          loaded active running   Disk Manager
  upower.service                                           loaded active running   Daemon for power management
  user-runtime-dir@1000.service                            loaded active exited    User Runtime Directory /run/user/1000
  user@1000.service                                        loaded active running   User Manager for UID 1000
  wpa_supplicant.service                                   loaded active running   WPA supplicant
  avahi-daemon.socket                                      loaded active running   Avahi mDNS/DNS-SD Stack Activation Socket
  clamav-daemon.socket                                     loaded active running   Socket for Clam AntiVirus userspace daemon
  cups.socket                                              loaded active running   CUPS Scheduler
  dbus.socket                                              loaded active running   D-Bus System Message Bus Socket
  dirmngr@etc-pacman.d-gnupg.socket                        loaded active listening GnuPG network certificate management daemon for /etc/pacman.d/gnupg
  dm-event.socket                                          loaded active listening Device-mapper event daemon FIFOs
  gpg-agent-browser@etc-pacman.d-gnupg.socket              loaded active listening GnuPG cryptographic agent and passphrase cache (access for web browsers) for /etc/pacman.d/gnupg
  gpg-agent-extra@etc-pacman.d-gnupg.socket                loaded active listening GnuPG cryptographic agent and passphrase cache (restricted) for /etc/pacman.d/gnupg
  gpg-agent-ssh@etc-pacman.d-gnupg.socket                  loaded active listening GnuPG cryptographic agent (ssh-agent emulation) for /etc/pacman.d/gnupg
  gpg-agent@etc-pacman.d-gnupg.socket                      loaded active listening GnuPG cryptographic agent and passphrase cache for /etc/pacman.d/gnupg
  keyboxd@etc-pacman.d-gnupg.socket                        loaded active listening GnuPG public key management service for /etc/pacman.d/gnupg
  lvm2-lvmpolld.socket                                     loaded active listening LVM2 poll daemon socket
  sshd-unix-local.socket                                   loaded active listening OpenSSH Server Socket (systemd-ssh-generator, AF_UNIX Local)
  systemd-bootctl.socket                                   loaded active listening Boot Entries Service Socket
  systemd-coredump.socket                                  loaded active listening Process Core Dump Socket
  systemd-creds.socket                                     loaded active listening Credential Encryption/Decryption
  systemd-hostnamed.socket                                 loaded active listening Hostname Service Socket
  systemd-importd.socket                                   loaded active listening Disk Image Download Service Socket
  systemd-journald-dev-log.socket                          loaded active running   Journal Socket (/dev/log)
  systemd-journald.socket                                  loaded active running   Journal Sockets
  systemd-sysext.socket                                    loaded active listening System Extension Image Management
  systemd-udevd-control.socket                             loaded active running   udev Control Socket
  systemd-udevd-kernel.socket                              loaded active running   udev Kernel Socket

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#2 2025-05-01 06:39:19

-thc
Member
Registered: 2017-03-15
Posts: 890

Re: Repeated temporary failures of domain name resolution

cfr wrote:

...but the only troubleshooting tip I've gleaned so far is that it might be good to ping 9.9.9.9 the next time resolution fails.

Since your error is consistent with an uplink failure hat is exactly what you need to do.

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#3 2025-05-01 07:07:30

seth
Member
Registered: 2012-09-03
Posts: 64,050

Re: Repeated temporary failures of domain name resolution

You can then (and assuming you can ping WAN IPs fine) also

dig @9.9.9.9 example.com
dig @194.168.4.100 example.com
dig @194.168.8.100 example.com
dig @192.168.5.1 example.com

If your router has no local DNS cache and (also) simply forwards the (often notoriously underdimensioned) ISP DNS servers, I'd not be surprised if those end up being the bottleneck and start to quota you.
You might want to switch to an open DNS server (quad9, cloudflare is 1.1.1.1, google 8.8.8.8) and look into a local cache like dnsmasq, stubby or resolved, https://wiki.archlinux.org/title/Domain … NS_servers

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#4 2025-05-01 07:58:10

cfr
Member
From: Cymru
Registered: 2011-11-27
Posts: 7,167

Re: Repeated temporary failures of domain name resolution

seth wrote:

You can then (and assuming you can ping WAN IPs fine) also

I can't successfully ping outside my LAN. e.g.

$ ping 9.9.9.9

fails.

systemctl status netctl-auto\@wlan0.service:

● netctl-auto@wlan0.service - Automatic wireless network connection using netctl profiles
     Loaded: loaded (/usr/lib/systemd/system/netctl-auto@.service; enabled; preset: disabled)
     Active: active (running) since Wed 2025-04-30 14:59:13 BST; 17h ago
 Invocation: 118095dd2d2b4fba98a831133f4f0554
       Docs: man:netctl.special(7)
    Process: 748 ExecStart=/usr/bin/netctl-auto start wlan0 (code=exited, status=0/SUCCESS)
      Tasks: 7 (limit: 9281)
     Memory: 4.2M (peak: 18.1M, swap: 2.6M, swap peak: 2.6M, zswap: 304.2K)
        CPU: 3.912s
     CGroup: /system.slice/system-netctl\x2dauto.slice/netctl-auto@wlan0.service
             ├─ 853 wpa_supplicant -q -B -P /run/wpa_supplicant-wlan0.pid -i wlan0 -D nl80211,wext -c/run/netctl/wpa_supplicant-wlan0.conf -W
             ├─ 857 wpa_cli -i wlan0 -p /run/wpa_supplicant -B -a /usr/lib/netctl/auto.action
             ├─1091 "dhcpcd: wlan0 [ip4]"
             ├─1092 "dhcpcd: [privileged proxy] wlan0 [ip4]"
             ├─1093 "dhcpcd: [control proxy] wlan0 [ip4]"
             ├─1096 "dhcpcd: [BPF ARP] wlan0 192.168.5.248"
             └─1155 "dhcpcd: [BOOTP proxy] 192.168.5.248"

Ebr 30 14:59:13 FyEnw systemd[1]: Started Automatic wireless network connection using netctl profiles.
Ebr 30 14:59:17 FyEnw dhcpcd[1089]: dhcpcd-10.2.2 starting
Ebr 30 14:59:17 FyEnw dhcpcd[1092]: DUID 00:01:00:01:2c:02:f6:13:f4:96:34:dc:aa:f5
Ebr 30 14:59:17 FyEnw dhcpcd[1092]: wlan0: connected to Access Point: Cartref Rees
Ebr 30 14:59:17 FyEnw dhcpcd[1092]: wlan0: IAID 34:dc:aa:f5
Ebr 30 14:59:17 FyEnw dhcpcd[1092]: wlan0: rebinding lease of 192.168.5.248
Ebr 30 14:59:21 FyEnw dhcpcd[1092]: wlan0: probing address 192.168.5.248/24
Ebr 30 14:59:26 FyEnw dhcpcd[1092]: wlan0: leased 192.168.5.248 for 86400 seconds
Ebr 30 14:59:26 FyEnw dhcpcd[1092]: wlan0: adding route to 192.168.5.0/24
Ebr 30 14:59:26 FyEnw dhcpcd[1092]: wlan0: adding default route via 192.168.5.1

systemctl status wpa_supplicant.service:

● wpa_supplicant.service - WPA supplicant
     Loaded: loaded (/usr/lib/systemd/system/wpa_supplicant.service; disabled; preset: disabled)
     Active: active (running) since Wed 2025-04-30 15:24:26 BST; 17h ago
 Invocation: 44ababad35af4bd1b7e5496811bb408a
   Main PID: 2410 (wpa_supplicant)
      Tasks: 1 (limit: 9281)
     Memory: 364K (peak: 1.7M, swap: 848K, swap peak: 848K, zswap: 121.6K)
        CPU: 257ms
     CGroup: /system.slice/wpa_supplicant.service
             └─2410 /usr/bin/wpa_supplicant -u -s -O /run/wpa_supplicant

Ebr 30 15:24:26 FyEnw systemd[1]: Starting WPA supplicant...
Ebr 30 15:24:26 FyEnw systemd[1]: Started WPA supplicant.
Ebr 30 15:24:26 FyEnw wpa_supplicant[2410]: Successfully initialized wpa_supplicant

But I do not understand why this is running at all? I understand netctl needs wpa_supplicant, but it doesn't obviously use the .service?

journalctrl: (firewall? but only sometimes?)

Mai 01 08:30:31 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53382 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:30:43 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53394 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:30:55 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53406 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:31:06 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53417 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:31:19 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53429 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:31:31 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53441 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:31:43 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53453 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:31:54 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53464 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:32:07 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53476 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:32:19 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53488 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:32:31 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53500 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:32:34 FyEnw clamd[670]: Thu May  1 08:32:34 2025 -> SelfCheck: Database status OK.
Mai 01 08:32:43 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53511 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:32:43 FyEnw kernel: IN=wlan0 OUT= MAC= SRC=fe80:0000:0000:0000:f696:34ff:fedc:aaf5 DST=ff02:0000:0000:0000:0000:0000:0000:00fb LEN=87 TC=0 HOPLIMIT=255 FLOWLBL=483608 PROTO=UDP SPT=5353 DPT=5353 LEN=47
Mai 01 08:32:55 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53523 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:33:07 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53535 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:33:19 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53547 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:33:31 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53558 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:33:43 FyEnw kwin_x11[2084]: kwin_core: XCB error: 152 (BadDamage), sequence: 38283, resource id: 19097601, major code: 143 (DAMAGE), minor code: 3 (Subtract)
Mai 01 08:33:43 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53570 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:33:54 FyEnw chromium[30304]: Fontconfig error: Cannot load default config file: No such file: (null)
Mai 01 08:33:55 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53582 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:34:07 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53594 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:34:17 FyEnw chromium[30343]: Fontconfig error: Cannot load default config file: No such file: (null)
Mai 01 08:34:19 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53605 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:34:31 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53617 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:34:43 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53629 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:34:55 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53640 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:35:07 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53652 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:35:19 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53664 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:35:30 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53675 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:35:43 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53687 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:35:55 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53699 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:36:07 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53711 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:36:18 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53722 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:36:31 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53734 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:36:43 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53746 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:36:55 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53758 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:37:07 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53769 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:37:19 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53781 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:37:31 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53793 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:37:42 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53804 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:37:55 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53816 PROTO=UDP SPT=11113 DPT=11111 LEN=138
Mai 01 08:38:07 FyEnw kernel: IN=wlan0 OUT= MAC=ff:ff:ff:ff:ff:ff:04:95:e6:63:96:80:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=158 TOS=0x00 PREC=0x00 TTL=64 ID=53828 PROTO=UDP SPT=11113 DPT=11111 LEN=138

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#5 2025-05-01 08:04:29

seth
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Registered: 2012-09-03
Posts: 64,050

Re: Repeated temporary failures of domain name resolution

This is the primary one of three Tenda WiFi cubes providing the WIFI LAN. It is connected to a router from the ISP which has WIFI disabled.

Can you still ping the modem?
If you don't know its IP check the first couple of hops in

tracepath example.com

do you have other hosts in that LAN that are not suffering from this?

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#6 2025-05-01 17:29:04

cfr
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From: Cymru
Registered: 2011-11-27
Posts: 7,167

Re: Repeated temporary failures of domain name resolution

seth wrote:

Can you still ping the modem?
If you don't know its IP check the first couple of hops in

tracepath example.com
$ tracepath example.com
 1?: [LOCALHOST]                      pmtu 1500
 1:  _gateway                                              3.395ms
 1:  _gateway                                              3.259ms
 2:  10.53.37.221                                         15.008ms
 3:  ???                                                  14.075ms
 4:  no reply
 5:  aor.uk-lon03a-ri1.network.virginmedia.net            19.003ms
 6:  no reply
 7:  ldn-bb2-link.ip.twelve99.net                         17.784ms
 8:  no reply
 9:  ash-bb2-link.ip.twelve99.net                        107.546ms asymm 11
10:  lax-b23-link.ip.twelve99.net                        163.964ms asymm 12
11:  akamai-ic-355471.ip.twelve99-cust.net               178.397ms asymm 14
12:  dls-bb2-link.ip.twelve99.net                        139.374ms asymm 16
13:  palo-b24-link.ip.twelve99.net                       161.944ms asymm 16
14:  sjo-b23-link.ip.twelve99.net                        155.856ms asymm 17
15:  a96-7-128-198.deploy.static.akamaitechnologies.com  153.494ms reached
     Resume: pmtu 1500 hops 15 back 20

I cannot ping 10.53.37.221 even when things are working.

do you have other hosts in that LAN that are not suffering from this?

Possibly. Other devices don't seem to suffer the same issue. However, my laptop is trying to connect far more than the other devices and it is a bit tricky to test because the problem typically doesn't last for very long. So when I've tested my phone, for example, I've connected OK. But when I've gone back to my laptop, that's been OK again, too, so I can't be sure the laptop was still having the problem when I tested the phone.

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#7 2025-05-01 19:47:31

seth
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Registered: 2012-09-03
Posts: 64,050

Re: Repeated temporary failures of domain name resolution

I cannot ping 10.53.37.221 even when things are working.

So the connection between the AP and the modem breaks down. Does either of them keep logs?

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#8 2025-05-02 12:41:19

cfr
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From: Cymru
Registered: 2011-11-27
Posts: 7,167

Re: Repeated temporary failures of domain name resolution

seth wrote:

I cannot ping 10.53.37.221 even when things are working.

So the connection between the AP and the modem breaks down. Does either of them keep logs?

Thanks. Hmm. I will try to find out. I'd be most surprised if the modem does. At least, I'd be surprised if our ISP provides a way to access it. So I will try the AP first.

But why can I not ping the address even when things are working? That does not make much sense to me?

And it turns out I can replicate the issue on other devices. But I failed to appreciate that 'no' meant 'yes' when interpreting the answers I was given sad.

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#9 2025-05-02 14:12:58

seth
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Registered: 2012-09-03
Posts: 64,050

Re: Repeated temporary failures of domain name resolution

But why can I not ping the address even when things are working? That does not make much sense to me?

Oh, the modem might simply ignore ICMP requests then - can you query it with nmap? (It probably runs dhcp on #53?)

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#10 2025-05-11 06:27:44

cfr
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From: Cymru
Registered: 2011-11-27
Posts: 7,167

Re: Repeated temporary failures of domain name resolution

This was a hardware problem on our ISP's side. So we now have a new router, some new connections and are plugged into a different socket in the box across the street.

The only problem is we now have two WIFI networks because the router is using default settings, but doesn't come with any instructions such as an IP address for configuration. Well, that and I'm curious if there is a way to establish its existence since it doesn't respond to pings ...

seth wrote:

Oh, the modem might simply ignore ICMP requests then - can you query it with nmap? (It probably runs dhcp on #53?)

No, but possibly I'm using it wrongly.

$ nmap 10.53.37.221
Starting Nmap 7.95 ( https://nmap.org ) at 2025-05-11 07:22 BST
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.04 seconds
$ nmap -Pn 10.53.37.221
Starting Nmap 7.95 ( https://nmap.org ) at 2025-05-11 07:20 BST
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.04 seconds
$ nmap -A -T4 10.53.37.221
Starting Nmap 7.95 ( https://nmap.org ) at 2025-05-11 07:21 BST
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 2.20 seconds

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#11 2025-05-11 11:55:57

seth
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Registered: 2012-09-03
Posts: 64,050

Re: Repeated temporary failures of domain name resolution

The modem IP might have changed w/ the overall reconfiguration.

ip r

- the default route is hopefully your new router wink
And have you tried "nmap -Pn _gateway" for the new router?
Though a consumer router w/o a webinterface sounds wild, telnet or ssh might be open.

However that's not helpful when you've to provide login creds that are not printed onto the bottom of the router.
googling the brand might reveal default credentials (though static defaults are illegal in the EU - dunno whether you brexited out of that mandate tongue)

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