An Ubuntu 19.10 machine has been experiencing sudden loss of network connectivity. It is on the same network as several Windows and Mac systems which never experience these network problems.
When the Ubuntu system experience this problem, running ping google.com will give the error message:
Temporary failure in name resolution
Tried running sudo dhclient to regain network connectivity. This sometimes solves the problem, and other times it just hangs there for a really long time.
Rebooting the system tends to work at restoring the network access, but the problem will eventually occur again.
What is really happening, and how can we avoid this problem?
ip route
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
172.18.0.0/16 dev br-e679420ceeeb proto kernel scope link src 172.18.0.1
172.19.0.0/16 dev br-d24de0d39a51 proto kernel scope link src 172.19.0.1
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: enp35s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
link/ether 70:85:c2:fd:cb:f9 brd ff:ff:ff:ff:ff:ff
3: enp36s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 70:85:c2:fd:e4:2b brd ff:ff:ff:ff:ff:ff
6: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default
link/ether 02:42:63:e9:39:70 brd ff:ff:ff:ff:ff:ff
19: br-e679420ceeeb: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default
link/ether 02:42:b0:9b:ad:ed brd ff:ff:ff:ff:ff:ff
20: br-d24de0d39a51: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default
link/ether 02:42:db:94:c2:16 brd ff:ff:ff:ff:ff:ff
22: veth88fb62f@if21: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-d24de0d39a51 state UP mode DEFAULT group default
link/ether 3a:f6:09:94:16:38 brd ff:ff:ff:ff:ff:ff link-netnsid 2
24: vethd4b4b3e@if23: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-e679420ceeeb state UP mode DEFAULT group default
link/ether 82:9c:8a:ea:fb:5c brd ff:ff:ff:ff:ff:ff link-netnsid 0
26: vethe937672@if25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-d24de0d39a51 state UP mode DEFAULT group default
link/ether 92:f9:2d:6c:50:f1 brd ff:ff:ff:ff:ff:ff link-netnsid 1
30: vetha7a98be@if29: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-e679420ceeeb state UP mode DEFAULT group default
link/ether ea:5b:cf:3a:71:82 brd ff:ff:ff:ff:ff:ff link-netnsid 3
32: veth35b48e4@if31: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-d24de0d39a51 state UP mode DEFAULT group default
link/ether 86:96:63:9a:a5:e0 brd ff:ff:ff:ff:ff:ff link-netnsid 5
33: enp3s0f0u14u2c2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 66:cb:3b:51:7d:87 brd ff:ff:ff:ff:ff:ff
cat /etc/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "resolvectl status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs must not access this file directly, but only through the
# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,
# replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.
nameserver 127.0.0.53
options edns0
cat /etc/nsswitch.conf
# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.
passwd: files systemd
group: files systemd
shadow: files
gshadow: files
hosts: files mdns4_minimal [NOTFOUND=return] dns
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis
nslookup ubuntu.com
Server: 127.0.0.53
Address: 127.0.0.53#53
** server can't find ubuntu.com: SERVFAIL
dig bing.com
; <<>> DiG 9.11.5-P4-5.1ubuntu2.1-Ubuntu <<>> bing.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 50385
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;bing.com. IN A
;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Mon Apr 06 18:21:13 EDT 2020
;; MSG SIZE rcvd: 37
systemd-resolve --status
Global
LLMNR setting: no
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
DNSSEC NTA: 10.in-addr.arpa
16.172.in-addr.arpa
168.192.in-addr.arpa
17.172.in-addr.arpa
18.172.in-addr.arpa
19.172.in-addr.arpa
20.172.in-addr.arpa
21.172.in-addr.arpa
22.172.in-addr.arpa
23.172.in-addr.arpa
24.172.in-addr.arpa
25.172.in-addr.arpa
26.172.in-addr.arpa
27.172.in-addr.arpa
28.172.in-addr.arpa
29.172.in-addr.arpa
30.172.in-addr.arpa
31.172.in-addr.arpa
corp
d.f.ip6.arpa
home
internal
intranet
lan
local
private
test
Link 33 (enp3s0f0u14u2c2)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 32 (veth35b48e4)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 30 (vetha7a98be)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 26 (vethe937672)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 24 (vethd4b4b3e)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 22 (veth88fb62f)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 20 (br-d24de0d39a51)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 19 (br-e679420ceeeb)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 6 (docker0)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 3 (enp36s0)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 2 (enp35s0)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
cat /var/log/syslog | grep resolved
Apr 6 00:00:01 foo-bar systemd-resolved[2390]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
Apr 6 00:00:01 foo-bar systemd-resolved[2390]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
Apr 6 00:00:01 foo-bar systemd-resolved[2390]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
Apr 6 00:00:01 foo-bar systemd-resolved[2390]: message repeated 2 times: [ Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.]
Apr 6 12:40:31 foo-bar systemd-resolved[2358]: Positive Trust Anchors:
Apr 6 12:40:31 foo-bar systemd-resolved[2358]: . IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607a1a41855200fd2ce1cdde32f24e8fb5
Apr 6 12:40:31 foo-bar systemd-resolved[2358]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc683457104237c7f8ec8d
Apr 6 12:40:31 foo-bar systemd-resolved[2358]: Negative trust anchors: 10.in-addr.arpa 16.172.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa 168.192.in-addr.arpa d.f.ip6.arpa corp home internal intranet lan local private test
Apr 6 12:40:31 foo-bar systemd-resolved[2358]: Using system hostname 'foo-bar'.
Apr 6 12:40:31 foo-bar NetworkManager[2489]: <info> [1586191231.7026] Read config: /etc/NetworkManager/NetworkManager.conf (lib: 10-dns-resolved.conf, 10-globally-managed-devices.conf, no-mac-addr-change.conf) (run: netplan.conf) (etc: default-wifi-powersave-on.conf)
Apr 6 12:40:31 foo-bar systemd-resolved[2358]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
Apr 6 12:40:31 foo-bar systemd-resolved[2358]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
Apr 6 12:40:31 foo-bar systemd-resolved[2358]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
Apr 6 12:40:31 foo-bar NetworkManager[2489]: <info> [1586191231.9621] dns-mgr[0x56555788b290]: init: dns=systemd-resolved rc-manager=symlink, plugin=systemd-resolved
Apr 6 12:40:32 foo-bar dockerd[2624]: time="2020-04-06T12:40:32.149982460-04:00" level=info msg="detected 127.0.0.53 nameserver, assuming systemd-resolved, so using resolv.conf: /run/systemd/resolve/resolv.conf"
Apr 6 18:11:51 foo-bar systemd[1]: systemd-resolved.service: Succeeded.
Apr 6 18:11:51 foo-bar systemd-resolved[8952]: Positive Trust Anchors:
Apr 6 18:11:51 foo-bar systemd-resolved[8952]: . IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607a1a41855200fd2ce1cdde32f24e8fb5
Apr 6 18:11:51 foo-bar systemd-resolved[8952]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc683457104237c7f8ec8d
Apr 6 18:11:51 foo-bar systemd-resolved[8952]: Negative trust anchors: 10.in-addr.arpa 16.172.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa 168.192.in-addr.arpa d.f.ip6.arpa corp home internal intranet lan local private test
Apr 6 18:11:51 foo-bar systemd-resolved[8952]: Using system hostname 'foo-bar'.
0 Answers