[195583] in North American Network Operators' Group
Re: Google DNS --- Figuring out which DNS Cluster you are using
daemon@ATHENA.MIT.EDU (i mawsog via NANOG)
Mon Aug 28 16:22:33 2017
X-Original-To: nanog@nanog.org
Date: Wed, 23 Aug 2017 20:37:32 +0000 (UTC)
To: "ESundberg@nitelusa.com" <ESundberg@nitelusa.com>,
"nanog@nanog.org" <nanog@nanog.org>
In-Reply-To: <495D0934DA46854A9CA758393724D590A5FD813E@NI-MAIL02.nii.ads>
From: i mawsog via NANOG <nanog@nanog.org>
Reply-To: "imawsog@yahoo.com" <imawsog@yahoo.com>
Errors-To: nanog-bounces@nanog.org
This is great. =C2=A0Thanks for sharing .=C2=A0
Sent from Yahoo Mail on Android=20
=20
On Wed, Aug 23, 2017 at 1:11 PM, Erik Sundberg<ESundberg@nitelusa.com> wr=
ote: I sent this out on the outage list, with a lots of good feedback sen=
t to me. So I figured it would be useful to share the information on nanog =
as well.
A couple months ago had to troubleshoot a google DNS issue with Google=E2=
=80=99s NOC. Below is some helpful information on how to determine which DN=
S Cluster you are going to.
Let=E2=80=99s remember that Google runs DNS Anycast for DNS queries to 8.8.=
8.8 and 8.8.4.4. Anycast routes your DNS queries to the closes DNS cluster =
based on the best route / lowest metric to 8.8.8.8/8.8.4.4.=C2=A0 Google ha=
s deployed multiple DNS clusters across the world and each DNS Cluster has =
multiple servers.
So a DNS query in Chicago will go to a different DNS clusters than queries =
from a device in Atlanta or New York.
How to get a list of google DNS Cluster=E2=80=99s.
dig -t TXT +short locations.publicdns.goog. @8.8.8.8
How to print this list in a table format. Script from: https://developers.g=
oogle.com/speed/public-dns/faq
---------------
#!/bin/bash
IFS=3D"\"$IFS"
for LOC in $(dig -t TXT +short locations.publicdns.goog. @8.8.8.8)
do
=C2=A0 case $LOC in
=C2=A0 =C2=A0 '') : ;;
=C2=A0 =C2=A0 *.*|*:*) printf '%s ' ${LOC} ;;
=C2=A0 =C2=A0 *) printf '%s\n' ${LOC} ;;
=C2=A0 esac
done
---------------
Which will give you a list like below. This is all of the IP network=E2=80=
=99s that google uses for their DNS Clusters and their associated locations=
.
74.125.18.0/26 iad
74.125.18.64/26 iad
74.125.18.128/26 syd
74.125.18.192/26 lhr
74.125.19.0/24 mrn
74.125.41.0/24 tpe
74.125.42.0/24 atl
74.125.44.0/24 mrn
74.125.45.0/24 tul
74.125.46.0/24 lpp
74.125.47.0/24 bru
74.125.72.0/24 cbf
74.125.73.0/24 bru
74.125.74.0/24 lpp
74.125.75.0/24 chs
74.125.76.0/24 cbf
74.125.77.0/24 chs
74.125.79.0/24 lpp
74.125.80.0/24 dls
74.125.81.0/24 dub
74.125.92.0/24 mrn
74.125.93.0/24 cbf
74.125.112.0/24 lpp
74.125.113.0/24 cbf
74.125.115.0/24 tul
74.125.176.0/24 mrn
74.125.177.0/24 atl
74.125.179.0/24 cbf
74.125.181.0/24 bru
74.125.182.0/24 cbf
74.125.183.0/24 cbf
74.125.184.0/24 chs
74.125.186.0/24 dls
74.125.187.0/24 dls
74.125.190.0/24 sin
74.125.191.0/24 tul
172.217.32.0/26 lhr
172.217.32.64/26 lhr
172.217.32.128/26 sin
172.217.33.0/26 syd
172.217.33.64/26 syd
172.217.33.128/26 fra
172.217.33.192/26 fra
172.217.34.0/26 fra
172.217.34.64/26 bom
172.217.34.192/26 bom
172.217.35.0/24 gru
172.217.36.0/24 atl
172.217.37.0/24 gru
173.194.90.0/24 cbf
173.194.91.0/24 scl
173.194.93.0/24 tpe
173.194.94.0/24 cbf
173.194.95.0/24 tul
173.194.97.0/24 chs
173.194.98.0/24 lpp
173.194.99.0/24 tul
173.194.100.0/24 mrn
173.194.101.0/24 tul
173.194.102.0/24 atl
173.194.103.0/24 cbf
173.194.168.0/26 nrt
173.194.168.64/26 nrt
173.194.168.128/26 nrt
173.194.168.192/26 iad
173.194.169.0/24 grq
173.194.170.0/24 grq
173.194.171.0/24 tpe
2404:6800:4000::/48 bom
2404:6800:4003::/48 sin
2404:6800:4006::/48 syd
2404:6800:4008::/48 tpe
2404:6800:400b::/48 nrt
2607:f8b0:4001::/48 cbf
2607:f8b0:4002::/48 atl
2607:f8b0:4003::/48 tul
2607:f8b0:4004::/48 iad
2607:f8b0:400c::/48 chs
2607:f8b0:400d::/48 mrn
2607:f8b0:400e::/48 dls
2800:3f0:4001::/48 gru
2800:3f0:4003::/48 scl
2a00:1450:4001::/48 fra
2a00:1450:4009::/48 lhr
2a00:1450:400b::/48 dub
2a00:1450:400c::/48 bru
2a00:1450:4010::/48 lpp
2a00:1450:4013::/48 grq
There are
IPv4 Networks: 68
IPv6 Networks: 20
DNS Cluster=E2=80=99s Identified by POP Code=E2=80=99s: 20
DNS Clusters identified by POP Code to City, State, or Country. Not all of =
these are Google=E2=80=99s Core Datacenters, some of them are Edge Points o=
f Presences (POPs). https://peering.google.com/#/infrastructure and https:/=
/www.google.com/about/datacenters/inside/locations/
Most of these are airport codes, it did my best to get the location correct=
.
iad=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Washington, DC
syd=C2=A0 =C2=A0 =C2=A0 =C2=A0 Sydney, Australia
lhr=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 London, UK
mrn=C2=A0 =C2=A0 =C2=A0 =C2=A0 Lenoir, NC
tpe=C2=A0 =C2=A0 =C2=A0 =C2=A0 Taiwan
atl=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Altanta, GA
tul=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Tulsa, OK
lpp=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Findland
bru=C2=A0 =C2=A0 =C2=A0 =C2=A0 Brussels, Belgium
cbf=C2=A0 =C2=A0 =C2=A0 =C2=A0 Council Bluffs, IA
chs=C2=A0 =C2=A0 =C2=A0 =C2=A0 Charleston, SC
dls=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 The Dalles, Oregon
dub=C2=A0 =C2=A0 =C2=A0 =C2=A0 Dublin, Ireland
sin=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Singapore
fra=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Frankfort, Germany
bom=C2=A0 =C2=A0 =C2=A0 Mumbai, India
gru=C2=A0 =C2=A0 =C2=A0 =C2=A0 Sao Paulo, Brazil
scl=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Santiago, Chile
nrt=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Tokyo, Japan
grq=C2=A0 =C2=A0 =C2=A0 =C2=A0 Groningen, Netherlans
Which Google DNS Server Cluster am I using. I am testing this from Chicago,=
IL
# dig o-o.myaddr.l.google.com -t txt +short @8.8.8.8
"173.194.94.135"=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 <<<<<<DNS Server IP, reference the list above to get the cluster=
, Council Bluffs, IA
"edns0-client-subnet 207.xxx.xxx.0/24"=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 <<<< Your Source IP Block
Side note, the google dns servers will not respond to DNS queries to the Cl=
uster=E2=80=99s Member=E2=80=99s IP, they will only respond to dns queries =
to 8.8.8.8 and 8.8.4.4. So the following will not work.
dig google.com @173.194.94.135
Now to see the DNS Cluster load balancing in action. I am doing a dig query=
from our Telx\Digital Realty POP in Atlanta, GA. We do peer with google at=
this location.
I dig a dig query about 10 times and received the following unique dns clus=
ter member ip=E2=80=99s as responses.
dig o-o.myaddr.l.google.com -t txt +short @8.8.8.8
"74.125.42.138"
"173.194.102.132"
"74.125.177.5"
"74.125.177.74"
"74.125.177.71"
"74.125.177.4"
Which all are Google DNS Networks in Atlanta.
74.125.42.0/24
atl
74.125.177.0/24
atl
172.217.36.0/24
atl
173.194.102.0/24
atl
2607:f8b0:4002::/48
atl
Just thought it would be helpful when troubleshooting google DNS issues.
________________________________
CONFIDENTIALITY NOTICE: This e-mail transmission, and any documents, files =
or previous e-mail messages attached to it may contain confidential informa=
tion that is legally privileged. If you are not the intended recipient, or =
a person responsible for delivering it to the intended recipient, you are h=
ereby notified that any disclosure, copying, distribution or use of any of =
the information contained in or attached to this transmission is STRICTLY P=
ROHIBITED. If you have received this transmission in error please notify th=
e sender immediately by replying to this e-mail. You must destroy the origi=
nal transmission and its attachments without reading or saving in any manne=
r. Thank you.
=20
