为什么默认的 Ubuntu LTS 安装不允许host -6 gnu.org或dig -6 gnu.org无法工作？
Welcome to Ubuntu 22.04 LTS (GNU/Linux 5.15.0-27-generic x86_64)
$ host -6 gnu.org
;; communications error to ::1#53: connection refused
$ dig -6 gnu.org
;; communications error to ::1#53: connection refused
存根解析器似乎只监听 IPv4：
$ tail -3 /etc/resolv.conf
nameserver 127.0.0.53
options edns0 trust-ad
search home.idallen.ca
# netstat -nap | grep resolv
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN 603/systemd-resolve
udp 0 0 127.0.0.53:53 0.0.0.0:* 603/systemd-resolve
unix 2 [ ACC ] STREAM LISTENING 25992 603/systemd-resolve /run/systemd/resolve/io.systemd.Resolve
unix 2 [ ] DGRAM CONNECTED 25969 603/systemd-resolve
unix 3 [ ] STREAM CONNECTED 25989 603/systemd-resolve
unix 3 [ ] STREAM CONNECTED 23439 603/systemd-resolve
如何让 Ubuntu LTS 也在 IPv6 上监听，为什么这不是默认设置？
细节（为保护无辜者，部分 IP 地址已更改）：
我把我的机器放在我的有线 ISP 上，但它不工作，尽管我可以ping6随处ssh -6进出。
我把我的机器放在我的 DSL ISP 上，但它不工作，尽管我可以ping6随处ssh -6进出。
使用我的有线 ISP 的详细信息：
$ ping -c 1 -4 gnu.org
PING gnu.org (209.51.188.116) 56(84) bytes of data.
64 bytes from wildebeest1p.gnu.org (209.51.188.116): icmp_seq=1 ttl=55 time=29.4 ms
$ ping -c 1 -6 gnu.org
PING gnu.org(wildebeest1p.gnu.org (2001:470:142:5::116)) 56 data bytes
64 bytes from wildebeest1p.gnu.org (2001:470:142:5::116): icmp_seq=1 ttl=55 time=28.5 ms
$ host -4 gnu.org
gnu.org has address 209.51.188.116
gnu.org has IPv6 address 2001:470:142:5::116
gnu.org mail is handled by 10 eggs.gnu.org.
$ tail -3 /etc/resolv.conf
nameserver 127.0.0.53
options edns0 trust-ad
search phub.net.cable.rogers.com
$ resolvectl
Global
Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub
Link 2 (enp0s25)
Current Scopes: DNS
Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 64.71.255.204
DNS Servers: 64.71.255.204 64.71.255.198 2607:f798:18:10:0:640:7125:5204
2607:f798:18:10:0:640:7125:5198
2607:fea8:c2e0:86f0:494:35ff:fea4:dcba
DNS Domain: phub.net.cable.rogers.com
$ ip -6 route
::1 dev lo proto kernel metric 256 pref medium
2607:fea8:c2e0:86f0::abcd dev enp0s25 proto kernel metric 100 pref medium
2607:fea8:c2e0:86f0::/64 dev enp0s25 proto ra metric 100 pref medium
fe80::/64 dev enp0s25 proto kernel metric 1024 pref medium
default via fe80::494:35ff:fea4:dcba dev enp0s25 proto ra metric 20100 pref medium
$ host -6 gnu.org
;; communications error to ::1#53: connection refused
使用我的 DSL ISP 的详细信息（仅与 Cable 不同的部分）：
$ tail -3 /etc/resolv.conf
nameserver 127.0.0.53
options edns0 trust-ad
search home.idallen.ca
$ resolvectl
Global
Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub
Link 2 (enp0s25)
Current Scopes: DNS
Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 2607:f2c0::1
DNS Servers: 192.168.2.254 2607:f2c0::1 2607:f2c0::2
DNS Domain: home.idallen.ca
$ ip -6 route
::1 dev lo proto kernel metric 256 pref medium
2607:f2c0:f00e:5d00::/64 via fe80::3e90:66ff:fed4:acdb dev enp0s25 proto ra metric 100 pref high
fe80::/64 dev enp0s25 proto kernel metric 1024 pref medium
default via fe80::3e90:66ff:fed4:acdb dev enp0s25 proto ra metric 20100 pref low
$ host -6 gnu.org
;; communications error to ::1#53: connection refused