Hello! I talked to a couple of friends recently who mentioned they wished they knew
how to use
dig to make DNS queries, so here’s a quick blog post about it.
When I first started using
dig I found it a bit intimidating – there are so
many options! I’m going to leave out most of dig’s options in this post and just
talk about the ones I actually use.
Also I learned recently that you can set up a
.digrc configuration file to make its output
easier to read and it makes it SO MUCH nicer to use.
I also drew a zine page about dig a few years ago, but I wanted to write this post to include a bit more information.
2 types of dig arguments: query and formatting
There are 2 main types of arguments you can pass to
- arguments that tell dig what DNS query to make
- arguments that tell dig how to format the response
First, let’s go through the query options.
the main query options
The 3 things you usually want to control about a DNS query are:
- the name (like
jvns.ca). The default is a query for the empty name (
- the DNS query type (like
CNAME). The default is
- the server to send the query to (like
18.104.22.168). The default is what’s in
The format for these is:
dig @server type name
Here are a couple of examples:
dig @22.214.171.124 jvns.caqueries Google’s public DNS server (
dig ns jvns.camakes an query with type
-x: make a reverse DNS query
One other query option I use occasionally is
-x, to make a reverse DNS query. Here’s what the output looks like.
$ dig -x 126.96.36.199 188.8.131.52.in-addr.arpa. 72888 IN PTR yul03s04-in-f14.1e100.net.
-x isn’t magic –
dig -x 184.108.40.206 just makes a
PTR query for
220.127.116.11.in-addr.arpa.. Here’s how to make exact the same reverse DNS query
$ dig ptr 18.104.22.168.in-addr.arpa. 22.214.171.124.in-addr.arpa. 72888 IN PTR yul03s04-in-f14.1e100.net.
I always use
-x though because it’s less typing.
options for formatting the response
Now, let’s talk about arguments you can use to format the response.
I’ve found that the way
dig formats DNS responses by default is pretty
overwhelming to beginners. Here’s what the output looks like:
; <<>> DiG 9.16.20 <<>> -r jvns.ca ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28629 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ; COOKIE: d87fc3022c0604d60100000061ab74857110b908b274494d (good) ;; QUESTION SECTION: ;jvns.ca. IN A ;; ANSWER SECTION: jvns.ca. 276 IN A 126.96.36.199 ;; Query time: 9 msec ;; SERVER: 192.168.1.1#53(192.168.1.1) ;; WHEN: Sat Dec 04 09:00:37 EST 2021 ;; MSG SIZE rcvd: 80
If you’re not used to reading this, it might take you a while to sift through it and find the IP address you’re looking for.
And most of the time, you’re only interested in one line of this response (
jvns.ca. 276 IN A 188.8.131.52).
Here are my 2 favourite ways to make dig’s output more manageable.
way 1: +noall +answer
This tells dig to just print what’s in the “Answer” section of the DNS response. Here’s an example of querying for the
NS records for
$ dig +noall +answer ns google.com google.com. 158564 IN NS ns4.google.com. google.com. 158564 IN NS ns1.google.com. google.com. 158564 IN NS ns2.google.com. google.com. 158564 IN NS ns3.google.com.
The format here is:
NAME TTL TYPE CONTENT google.com 158564 IN NS ns3.google.com.
By the way: if you’ve ever wondered what
IN means, it’s the “query class” and
stands for “internet”. It’s basically just a relic from the 80s and 90s when
there were other networks competing with the internet like “chaosnet”.
way 2: +short
This is like
dig +noall +answer, but even shorter – it just shows the
content of each record. For example:
$ dig +short ns google.com ns2.google.com. ns1.google.com. ns4.google.com. ns3.google.com.
you can put formatting options in
If you don’t like dig’s default format (I don’t!), you can tell it
to use a different format by default by creating a
.digrc file in your home
I really like the
+noall +answer format, so I put
+noall +answer in my
~/.digrc. Here’s what it looks like for me when I run
dig jvns.ca using that
$ dig jvns.ca jvns.ca. 255 IN A 184.108.40.206
So much easier to read!
And if I want to go back to the long format with all of the output (which I do sometimes, usually because I want to look at the records in the Authority section of the response), I can get a long answer again by running:
$ dig +all jvns.ca
The last dig option that I use is
dig +trace mimics what a DNS
resolver does when it looks up a domain – it starts at the root nameservers,
and then queries the next level of nameservers (like
.com), and so on until it reaches the authoritative nameserver for the domain.
So it’ll make about 30 DNS queries. (I checked using tcpdump, it seems to make 2 queries to get A/AAAA records for each of the root nameservers so that’s already 26 queries. I’m not really sure why it does this because it should already have those IPs hardcoded, but it does.)
I find this mostly useful for understanding how DNS works though, I don’t think that I’ve used it to solve a problem.
Even though there are simpler tools to make DNS queries (like
I find myself sticking with dig.
What I like about dig is actually the same thing I don’t like about dig – it shows a lot of detail!
I know that if I run
dig +all, it’ll show me all of the sections of the DNS
response. For example, let’s query one of the root nameservers for
The response has 3 sections I might care about – Answer, Authority, and Additional.
$ dig @h.root-servers.net. jvns.ca +all ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18229 ;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 4, ADDITIONAL: 9 ;; WARNING: recursion requested but not available ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 1232 ;; QUESTION SECTION: ;jvns.ca. IN A ;; AUTHORITY SECTION: ca. 172800 IN NS c.ca-servers.ca. ca. 172800 IN NS j.ca-servers.ca. ca. 172800 IN NS x.ca-servers.ca. ca. 172800 IN NS any.ca-servers.ca. ;; ADDITIONAL SECTION: c.ca-servers.ca. 172800 IN A 220.127.116.11 j.ca-servers.ca. 172800 IN A 18.104.22.168 x.ca-servers.ca. 172800 IN A 22.214.171.124 any.ca-servers.ca. 172800 IN A 126.96.36.199 c.ca-servers.ca. 172800 IN AAAA 2620:10a:8053::2 j.ca-servers.ca. 172800 IN AAAA 2001:500:83::1 x.ca-servers.ca. 172800 IN AAAA 2620:10a:80ba::68 any.ca-servers.ca. 172800 IN AAAA 2001:500:a7::2 ;; Query time: 103 msec ;; SERVER: 188.8.131.52#53(184.108.40.206) ;; WHEN: Sat Dec 04 11:23:32 EST 2021 ;; MSG SIZE rcvd: 289
dog also shows the records in the “additional” section , but it’s not super explicit about
which is which (I guess the
+ means it’s in the additional section?). It
doesn’t seem to show the records in the “Authority” section.
$ dog @h.root-servers.net. jvns.ca NS ca. 2d0h00m00s A "c.ca-servers.ca." NS ca. 2d0h00m00s A "j.ca-servers.ca." NS ca. 2d0h00m00s A "x.ca-servers.ca." NS ca. 2d0h00m00s A "any.ca-servers.ca." A c.ca-servers.ca. 2d0h00m00s + 220.127.116.11 A j.ca-servers.ca. 2d0h00m00s + 18.104.22.168 A x.ca-servers.ca. 2d0h00m00s + 22.214.171.124 A any.ca-servers.ca. 2d0h00m00s + 126.96.36.199 AAAA c.ca-servers.ca. 2d0h00m00s + 2620:10a:8053::2 AAAA j.ca-servers.ca. 2d0h00m00s + 2001:500:83::1 AAAA x.ca-servers.ca. 2d0h00m00s + 2620:10a:80ba::68 AAAA any.ca-servers.ca. 2d0h00m00s + 2001:500:a7::2
host seems to only show the records in the “answer” section (in this case no records)
$ host jvns.ca h.root-servers.net Using domain server: Name: h.root-servers.net Address: 188.8.131.52#53 Aliases:
Anyway, I think that these simpler DNS tools are great (I even made my own simple web DNS tool) and you should
absolutely use them if you find them easier but that’s why I stick with dig.
drill’s output format seems very similar to
dig’s though, and maybe
is better! I haven’t really tried it.
I only learned about
.digrc recently and I love using it so much, so I hope
it helps some of you spend less time sorting though dig output!
Someone on Twitter pointed out that it would be nice if there were a way to
tell dig to show a short version of the response which also included the
response’s status (like
SERVFAIL, etc), and I agree! I
couldn’t find an option in the man page that does that though.