This is a text-only version of the following page on https://raymii.org:
---
Title : Match dig 127.0.0.53 server with systemd-resolvd server
Author : Remy van Elst
Date : 23-05-2019
URL : https://raymii.org/s/snippets/Match_dig_127.0.0.53_server_with_systemd-resolved_server.html
Format : Markdown/HTML
---
On systems that use `systemd-resolved` for DNS you will see the
`127.0.0.53` IP address in dig output. dig is a tool to do DNS lookups,
and for troubleshooting it's usefull to see which server is being queried.
With `systemd-resolved`, you need to issue another command to view the actual
server that is being queried, since `systemd-resolved` also acts as a local
caching server.
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### dig query
Using the following example of a default dig query you will see in the output a
line saying "SERVER", which is the server answering the query:
$ dig A raymii.org
; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> A raymii.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23416
;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;raymii.org. IN A
;; ANSWER SECTION:
raymii.org. 300 IN A 45.32.136.37
raymii.org. 300 IN A 80.211.96.38
raymii.org. 300 IN A 116.203.75.71
raymii.org. 300 IN A 199.19.225.3
raymii.org. 300 IN A 185.121.24.135
raymii.org. 300 IN A 212.47.241.60
raymii.org. 300 IN A 128.199.39.10
;; Query time: 12 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Thu May 23 09:07:29 CEST 2019
;; MSG SIZE rcvd: 151
This line:
;; SERVER: 127.0.0.53#53(127.0.0.53)
If we give dig a specific DNS server to query you will see that reflected in
the output:
$ dig A raymii.org @8.8.8.8
; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> A raymii.org @8.8.8.8
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 63820
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;raymii.org. IN A
;; ANSWER SECTION:
raymii.org. 286 IN A 116.203.75.71
raymii.org. 286 IN A 185.121.24.135
raymii.org. 286 IN A 212.47.241.60
raymii.org. 286 IN A 199.19.225.3
raymii.org. 286 IN A 45.32.136.37
raymii.org. 286 IN A 128.199.39.10
raymii.org. 286 IN A 80.211.96.38
;; Query time: 9 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Thu May 23 09:09:01 CEST 2019
;; MSG SIZE rcvd: 151
The line now reflects the google dns:
;; SERVER: 8.8.8.8#53(8.8.8.8)
### systemd-resolved
When debugging, for example when an internal DNS server gives different results,
you would want to know which internal dns server answered the request, instead
of seeing that it was your local resolver. If you are using `systemd-resolved`
(default on Ubuntu 18.04) the following command will show the actual upstream
DNS server (received from DHCP) used:
systemd-resolve --status | grep "DNS Servers"
Example output:
DNS Servers: 192.168.55.254
If you have more than one network interface you will need to look at the full
command output.
---
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