1

I was comparing outputs of the same DNS query performed using dig against Cloudflare's 1.1.1.1 and Google's 8.8.8.8 nameservers:

$> dig +trace +additional wikpedia.org @1.1.1.1

; <<>> DiG 9.16.1-Ubuntu <<>> +trace +additional wikipedia.org @1.1.1.1
;; global options: +cmd
.           512680  IN  NS  a.root-servers.net.
.           512680  IN  NS  b.root-servers.net.
.           512680  IN  NS  c.root-servers.net.
.           512680  IN  NS  d.root-servers.net.
.           512680  IN  NS  e.root-servers.net.
.           512680  IN  NS  f.root-servers.net.
.           512680  IN  NS  g.root-servers.net.
.           512680  IN  NS  h.root-servers.net.
.           512680  IN  NS  i.root-servers.net.
.           512680  IN  NS  j.root-servers.net.
.           512680  IN  NS  k.root-servers.net.
.           512680  IN  NS  l.root-servers.net.
.           512680  IN  NS  m.root-servers.net.
.           512680  IN  RRSIG   NS 8 0 518400 20221010050000 20220927040000 20826 . E5aHqAj0MqKBkUBMP7OC3GDjnnr2T1unuV9Qy29b4VAYj7onRsOJypPn MDlXlFx1PcnOxOR3ATfuJnvKp+e7jOTsX7XJNo3NKhlin+dzdL12q9Rg /D3kutjO6eDFBySaJU9fzt4yFa92hZclEiZSk87GkTZPfkV1k9exgP0U NszN9caQfChOt9/jS+0d8LAO9ZWdiPWeB+d/cXwm+wtE4YmV0eUjmuPw ZOGBLKX6EYSoYBm2gLK4ObAGb9OXgty5ub85RVdwTIIegRHHD0YisYYS 0YiPos4LCDlUgRDWIOicz4a44ThQ5Q59HuZmCgYCIJbGH8u2nmfcYPru xfv8Bw==
a.root-servers.net. 512680  IN  A   198.41.0.4
a.root-servers.net. 512680  IN  AAAA    2001:503:ba3e::2:30
b.root-servers.net. 512680  IN  A   199.9.14.201
b.root-servers.net. 512680  IN  AAAA    2001:500:200::b
c.root-servers.net. 512680  IN  A   192.33.4.12
c.root-servers.net. 512680  IN  AAAA    2001:500:2::c
d.root-servers.net. 512680  IN  A   199.7.91.13
d.root-servers.net. 512680  IN  AAAA    2001:500:2d::d
e.root-servers.net. 512680  IN  A   192.203.230.10
e.root-servers.net. 512680  IN  AAAA    2001:500:a8::e
f.root-servers.net. 512680  IN  A   192.5.5.241
f.root-servers.net. 512680  IN  AAAA    2001:500:2f::f
g.root-servers.net. 512680  IN  A   192.112.36.4
g.root-servers.net. 512680  IN  AAAA    2001:500:12::d0d
h.root-servers.net. 512680  IN  A   198.97.190.53
h.root-servers.net. 512680  IN  AAAA    2001:500:1::53
i.root-servers.net. 512680  IN  A   192.36.148.17
i.root-servers.net. 512680  IN  AAAA    2001:7fe::53
j.root-servers.net. 512680  IN  A   192.58.128.30
j.root-servers.net. 512680  IN  AAAA    2001:503:c27::2:30
k.root-servers.net. 512680  IN  A   193.0.14.129
k.root-servers.net. 512680  IN  AAAA    2001:7fd::1
l.root-servers.net. 512680  IN  A   199.7.83.42
l.root-servers.net. 512680  IN  AAAA    2001:500:9f::42
m.root-servers.net. 512680  IN  A   202.12.27.33
m.root-servers.net. 512680  IN  AAAA    2001:dc3::35
;; Received 1097 bytes from 1.1.1.1#53(1.1.1.1) in 16 ms

org.            172800  IN  NS  a0.org.afilias-nst.info.
org.            172800  IN  NS  a2.org.afilias-nst.info.
org.            172800  IN  NS  b0.org.afilias-nst.org.
org.            172800  IN  NS  b2.org.afilias-nst.org.
org.            172800  IN  NS  c0.org.afilias-nst.info.
org.            172800  IN  NS  d0.org.afilias-nst.org.
org.            86400   IN  DS  26974 8 2 4FEDE294C53F438A158C41D39489CD78A86BEB0D8A0AEAFF14745C0D 16E1DE32
org.            86400   IN  RRSIG   DS 8 1 86400 20221010050000 20220927040000 20826 . RdN/DLbZIJJuBD/GiDbrXN5dOdHfOicZgCJOH+FyHgySbHNgTOdd3YTx qd0+TkMw5Tn5ASYwv6Jgr7Z2IyAnEamhpPkWyAB0DKaaNq9fxPihLE7X gFw2rOZC3WoHuglasLa7hZ1sxVfezLjDFFLCZpAv1PIJtMJUTQhouHs+ tXWXVP9wtEaQpkB9lrvsqF3DJ2AXYRunjyQFeOyT89rFPuVOa810ZMJX 47JBe5L5NiPbJZ8w7+QXLdubOxiydBU6nLgIsbcwC1H3nmT70HI5B4QX TvMb++jeZZLSYGITuNxepg35Ej0yhEgtmG4EBLY0I7EFehJ4D+FrtfsE MhRHbg==
a0.org.afilias-nst.info. 172800 IN  A   199.19.56.1
a2.org.afilias-nst.info. 172800 IN  A   199.249.112.1
b0.org.afilias-nst.org. 172800  IN  A   199.19.54.1
b2.org.afilias-nst.org. 172800  IN  A   199.249.120.1
c0.org.afilias-nst.info. 172800 IN  A   199.19.53.1
d0.org.afilias-nst.org. 172800  IN  A   199.19.57.1
a0.org.afilias-nst.info. 172800 IN  AAAA    2001:500:e::1
a2.org.afilias-nst.info. 172800 IN  AAAA    2001:500:40::1
b0.org.afilias-nst.org. 172800  IN  AAAA    2001:500:c::1
b2.org.afilias-nst.org. 172800  IN  AAAA    2001:500:48::1
c0.org.afilias-nst.info. 172800 IN  AAAA    2001:500:b::1
d0.org.afilias-nst.org. 172800  IN  AAAA    2001:500:f::1
;; Received 779 bytes from 198.97.190.53#53(h.root-servers.net) in 32 ms

wikipedia.org.      3600    IN  NS  ns0.wikimedia.org.
wikipedia.org.      3600    IN  NS  ns1.wikimedia.org.
wikipedia.org.      3600    IN  NS  ns2.wikimedia.org.
gdtpongmpok61u9lvnipqor8lra9l4t0.org. 3600 IN NSEC3 1 1 0 332539EE7F95C32A GDTREA8KMJ2RNEQEN4M2OGJ26KFSUKJ7 NS SOA RRSIG DNSKEY NSEC3PARAM
tpeahq77pcfqu9h00c3mh570ah1f4g65.org. 3600 IN NSEC3 1 1 0 332539EE7F95C32A TPEESGJUPU0G7LLLUQEA296C6EAUG5AU NS DS RRSIG
gdtpongmpok61u9lvnipqor8lra9l4t0.org. 3600 IN RRSIG NSEC3 8 2 3600 20221018110348 20220927100348 56124 org. LEhQtnCo1BVvRmTpABXjHydO5iNF7TrLE2x2xeaaH2olcyVW8uKOsb5Y ReXZGbZOb43yHCk1vG0gQGrx2MBK5Oe/qi2SAunCMacS2bSmeXORkcfQ A/7jTngjUuT/BLuCWhztQ6zQW8cnn9UqJ5ORoE6kzt8K+jvgPgt06d7s yIo=
tpeahq77pcfqu9h00c3mh570ah1f4g65.org. 3600 IN RRSIG NSEC3 8 2 3600 20221016152907 20220925142907 56124 org. mnaJPzFSM+e5YbHREKLk/YTsOpnaJFO5aD2C18jAx1HJcn/a2huZFUil 2ig1CkHYDdbygYlfcKRmuW98h4QfJ3aGBDm8LBPWayC0Ehe1d8YHdzzE 9eZXZaiPhx13xwhOp4d9sGsRXs1OYNdwNO+Z+gxFY0bDJ9dduzt3PAtm /qw=
ns0.wikimedia.org.  3600    IN  A   208.80.154.238
ns1.wikimedia.org.  3600    IN  A   208.80.153.231
ns2.wikimedia.org.  3600    IN  A   91.198.174.239
;; Received 655 bytes from 199.249.112.1#53(a2.org.afilias-nst.info) in 244 ms

wikipedia.org.      600 IN  A   185.15.58.224
;; Received 78 bytes from 208.80.154.238#53(ns0.wikimedia.org) in 108 ms

and

$> dig +trace +additional wikpedia.org @8.8.8.8

; <<>> DiG 9.16.1-Ubuntu <<>> +trace +additional wikipedia.org @8.8.8.8
;; global options: +cmd
.           16129   IN  NS  m.root-servers.net.
.           16129   IN  NS  b.root-servers.net.
.           16129   IN  NS  c.root-servers.net.
.           16129   IN  NS  d.root-servers.net.
.           16129   IN  NS  e.root-servers.net.
.           16129   IN  NS  f.root-servers.net.
.           16129   IN  NS  g.root-servers.net.
.           16129   IN  NS  h.root-servers.net.
.           16129   IN  NS  i.root-servers.net.
.           16129   IN  NS  a.root-servers.net.
.           16129   IN  NS  j.root-servers.net.
.           16129   IN  NS  k.root-servers.net.
.           16129   IN  NS  l.root-servers.net.
.           16129   IN  RRSIG   NS 8 0 518400 20221009040000 20220926030000 20826 . Daw1Qe+tZFuaEP/Z6Dhp91rsDfVTNJ/exRtguZJt4NO2Jig/xuulcfai O5vkKFIn/nXPIkiMfk/UPZJn+08J8PCA8yFBjHRLmnAh25PFH6iDqjXb 192lMdeByCjEELw8P8YgzXXsPX1a526WiW9YmQtCsJfuFebqYV5lDVmI JRYwRd9Xsp8RHwfPMdG/UlVJQD+tVdf7VNaAuqA+VzNRWOYEAnkU8QVh INZqVBgSKV1/Zwi2SHrZxjRc3Zpo3NDXBRG9hQ/TXpf5IbyV9/TsVa1T M6p5/Eu7KsrRGhsoy6U6CeLrGhi7sXp0VehmW139ttQ4mmAnzBy7MrRc QNAYHg==
;; Received 525 bytes from 8.8.8.8#53(8.8.8.8) in 16 ms

org.            172800  IN  NS  b2.org.afilias-nst.org.
org.            172800  IN  NS  d0.org.afilias-nst.org.
org.            172800  IN  NS  a2.org.afilias-nst.info.
org.            172800  IN  NS  a0.org.afilias-nst.info.
org.            172800  IN  NS  b0.org.afilias-nst.org.
org.            172800  IN  NS  c0.org.afilias-nst.info.
org.            86400   IN  DS  26974 8 2 4FEDE294C53F438A158C41D39489CD78A86BEB0D8A0AEAFF14745C0D 16E1DE32
org.            86400   IN  RRSIG   DS 8 1 86400 20221010050000 20220927040000 20826 . RdN/DLbZIJJuBD/GiDbrXN5dOdHfOicZgCJOH+FyHgySbHNgTOdd3YTx qd0+TkMw5Tn5ASYwv6Jgr7Z2IyAnEamhpPkWyAB0DKaaNq9fxPihLE7X gFw2rOZC3WoHuglasLa7hZ1sxVfezLjDFFLCZpAv1PIJtMJUTQhouHs+ tXWXVP9wtEaQpkB9lrvsqF3DJ2AXYRunjyQFeOyT89rFPuVOa810ZMJX 47JBe5L5NiPbJZ8w7+QXLdubOxiydBU6nLgIsbcwC1H3nmT70HI5B4QX TvMb++jeZZLSYGITuNxepg35Ej0yhEgtmG4EBLY0I7EFehJ4D+FrtfsE MhRHbg==
d0.org.afilias-nst.org. 172800  IN  A   199.19.57.1
c0.org.afilias-nst.info. 172800 IN  A   199.19.53.1
b2.org.afilias-nst.org. 172800  IN  A   199.249.120.1
b0.org.afilias-nst.org. 172800  IN  A   199.19.54.1
a2.org.afilias-nst.info. 172800 IN  A   199.249.112.1
a0.org.afilias-nst.info. 172800 IN  A   199.19.56.1
d0.org.afilias-nst.org. 172800  IN  AAAA    2001:500:f::1
c0.org.afilias-nst.info. 172800 IN  AAAA    2001:500:b::1
b2.org.afilias-nst.org. 172800  IN  AAAA    2001:500:48::1
b0.org.afilias-nst.org. 172800  IN  AAAA    2001:500:c::1
a2.org.afilias-nst.info. 172800 IN  AAAA    2001:500:40::1
a0.org.afilias-nst.info. 172800 IN  AAAA    2001:500:e::1
;; Received 810 bytes from 192.36.148.17#53(i.root-servers.net) in 36 ms

wikipedia.org.      3600    IN  NS  ns1.wikimedia.org.
wikipedia.org.      3600    IN  NS  ns0.wikimedia.org.
wikipedia.org.      3600    IN  NS  ns2.wikimedia.org.
gdtpongmpok61u9lvnipqor8lra9l4t0.org. 3600 IN NSEC3 1 1 0 332539EE7F95C32A GDTREA8KMJ2RNEQEN4M2OGJ26KFSUKJ7 NS SOA RRSIG DNSKEY NSEC3PARAM
gdtpongmpok61u9lvnipqor8lra9l4t0.org. 3600 IN RRSIG NSEC3 8 2 3600 20221018110920 20220927100920 56124 org. iwWHasNQhI07eGqMt4x8wd/Cnpmz+uggD/ArES2+Dpb44wCkVbC2oNGg rnPRoCyIi2YU+aVeZOmrDA8l2P3DNGT9R/pt0HT6Si098ZRjYSU0zZJj N4b1RWf/qtIS25z82jFjYh/NW4aPURpFZPL3Jg+UJkDAOarX0ZyzHHtA uM8=
tpeahq77pcfqu9h00c3mh570ah1f4g65.org. 3600 IN NSEC3 1 1 0 332539EE7F95C32A TPEESGJUPU0G7LLLUQEA296C6EAUG5AU NS DS RRSIG
tpeahq77pcfqu9h00c3mh570ah1f4g65.org. 3600 IN RRSIG NSEC3 8 2 3600 20221016152907 20220925142907 56124 org. mnaJPzFSM+e5YbHREKLk/YTsOpnaJFO5aD2C18jAx1HJcn/a2huZFUil 2ig1CkHYDdbygYlfcKRmuW98h4QfJ3aGBDm8LBPWayC0Ehe1d8YHdzzE 9eZXZaiPhx13xwhOp4d9sGsRXs1OYNdwNO+Z+gxFY0bDJ9dduzt3PAtm /qw=
ns0.wikimedia.org.  3600    IN  A   208.80.154.238
ns1.wikimedia.org.  3600    IN  A   208.80.153.231
ns2.wikimedia.org.  3600    IN  A   91.198.174.239
;; Received 655 bytes from 199.19.56.1#53(a0.org.afilias-nst.info) in 244 ms

wikipedia.org.      600 IN  A   185.15.58.224
;; Received 78 bytes from 91.198.174.239#53(ns2.wikimedia.org) in 32 ms

I was puzzled by the fact that Cloudflare's answer contains A and AAAA records while Google's does not.

Digging deeper, I found a BIND knowledge base article (https://kb.isc.org/docs/aa-00208) explaining the following:

When following delegation iteratively as specified with the +trace option, dig will begin by requesting the NS records for the servers authoritative for root ("."). These may or may not be supplied with glue - that is A and AAAA records that can be used for the next queries dig has to send. When there is no glue provided, either on the initial query for the root nameservers, or later on when following delegation, dig will revert to recursively querying the servers listed in /etc/resolv.conf to obtain the needed A/AAAA RRsets

Thus, my conclusion is that Google's 8.8.8.8 does not return glue when queried about the name servers for the root zone.

Is my conclusion correct or am I missing something?

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1 Answer 1

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The DNS name server responds with a name server’s domain name (NS record). To reach it, this name needs first to be resolved. Only having the domain name is not enough, thus NS records are accompanied by additional A records such as for the IP. These additional records are the glue records.

For root-servers this information is not required - you already know their IP address, so this is entirely optional. According to your tests, Google's servers are just more economical on their answer for the root-servers.

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3
  • Thanks for your answer! I'm aware that A records are needed in order to reach a given nameserver, and that DNS server's cache is "primed" with the A records for the root-servers (at least, so does BIND9 as per this article). What I am looking for is confirmation whether the result of my tests prove that 8.8.8.8's answer does not contain glue records or not.
    – gorgeous.george
    Sep 27, 2022 at 15:11
  • I wouldn't say that it "does not contain glue records", but rather that it chooses not to generate them. Google (and any other) certainly does have the information.
    – harrymc
    Sep 27, 2022 at 15:36
  • When I say it "does not contain glue records" I am referring to the answer received from the 8.8.8.8 server: so I think your answer confirms my conclusion. I'll accept your answer. Thanks
    – gorgeous.george
    Sep 27, 2022 at 21:59

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