I have DDWRT based WiFi router and affected the same bug.
DHCP6 as well as DNS6 in the router are disabled.
My problem was, that local DNS names provided by router stop resolved
after few minutes since reconnecting to the router WiFi or LAN, while
global domain names seems always resolved fine.
Bypassing systemd-resolve by editing manually nameservers in the
/etc/resolv.conf which is linked to the ../run/systemd/resolve/stub-
resolv.conf can fix the problem with local DNS names.
First I tried, as it was suggested in some discussions of the similar
issue, without success to set DNSSEC=no explicitly. Seems this systemd-
resolve setting is default now.
Then I tried to set DNS servers manually in the Network Manager. This didn't
help also.
Here the output when local DNS names provided by router stop resolved.
---------------8<----------------
$ 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 3 (wlp1s0)
Current Scopes: DNS
DefaultRoute setting: yes
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Current DNS Server: fe80::22cf:30ff:fece:c98
DNS Servers: 172.20.1.250
172.20.1.1
8.8.8.8
fe80::22cf:30ff:fece:c98
DNS Domain: ~.
lan
Link 2 (enp3s0f0)
Current Scopes: none
DefaultRoute setting: no
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
---------------8<----------------
Any idea what was the IP v6 DNS server address fe80::22cf:30ff:fece:c98
assigned?
I fixed the problem by changing Network Manager IP v6 mode setting from
Automatic to Ignore.
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https://bugs.launchpad.net/bugs/1865474
Title:
sysytemd-resolved automatically use an ipv6 dns server on lan
Status in systemd package in Ubuntu:
Confirmed
Bug description:
lsb_release -rd
Description: Ubuntu Focal Fossa (development branch)
Release: 20.04
i installed focal from the netboot version mini.iso.
i encountered some problem on dsn configuration and i found that
systemd-resolved was using an ipv6 dns address
this is my netplan configuration:
network:
version: 2
renderer: networkd
ethernets:
ens3:
addresses:
- 192.168.1.1/24
gateway4: 192.168.1.212
nameservers:
search: [xxx.com]
addresses: [192.168.1.191, 192.168.1.206]
this is the output of "systemd-resolved --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 2 (ens3)
Current Scopes: DNS
DefaultRoute setting: yes
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Current DNS Server: fe80::6670:2ff:feb5:d9c8
DNS Servers: 192.168.1.191
192.168.1.206
fe80::6670:2ff:feb5:d9c8
DNS Domain: xxx.com
--
as you can see systemd is using the ipv6 dns server.
i found that such ip was the address of my openwrt wifi router. dnsmasq is
disabled for ipv4 lan interface on the router and i never configured an ipv6
network. Anyway i disabled all the ipv6 dnsmasq feature on the router and after
a restart this fixed the problem.
But i think that this is a bug.
In my netplan i never configured an ipv6 dns nor a ipv6 network; furthermore
none of my other ubuntu bionic servers showed such a behaviour.
Also another focal netboot installation i made three weeks ago didn't show
this problem.
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