Google DNS --- Figuring out which DNS Cluster you are using

Thu Aug 24 00:30:03 UTC 2017

Gee Chris, that's kind of an asinine response.  Erik took the time to let
us know about what he had found out, with a nice code snippet too.  I don't
have time in my job to just go surfing around google.com to see what is
there.  His mail took me about 2 minutes to read and now I know that such
info exists.

Thank you Erik!

--
Joe Hamelin, W7COM, Tulalip, WA, +1 (360) 474-7474

On Wed, Aug 23, 2017 at 5:10 PM, Christopher Morrow <morrowc.lists at gmail.com
> wrote:

> On Wed, Aug 23, 2017 at 4:37 PM, i mawsog via NANOG <nanog at nanog.org>
> wrote:
>
> >
> > This is great.  Thanks for sharing .
> >
> > Sent from Yahoo Mail on Android
> >
> >   On Wed, Aug 23, 2017 at 1:11 PM, Erik Sundberg<ESundberg at nitelusa.com>
> > wrote:   I sent this out on the outage list, with a lots of good feedback
> > sent 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’s
> > NOC. Below is some helpful information on how to determine which DNS
> > Cluster you are going to.
> >
> > Let’s 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.  Google has 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’s.
> > dig -t TXT +short locations.publicdns.goog. @8.8.8.8
> >
> > How to print this list in a table format. Script from:
> > https://developers.google.com/speed/public-dns/faq
> > ---------------
> > #!/bin/bash
> > IFS="\"$IFS"
> > for LOC in $(dig -t TXT +short locations.publicdns.goog. @8.8.8.8)
> > do
> >   case $LOC in
> >     '') : ;;
> >     *.*|*:*) printf '%s ' ${LOC} ;;
> >     *) printf '%s\n' ${LOC} ;;
> >   esac
> > done
> > ---------------
> >
> > Which will give you a list like below. This is all of the IP network’s
> > 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
> >
> >
> isn't this list also here:
> https://developers.google.com/speed/public-dns/faq#locations
>
> I mean, you could read the docs first to get the same answer, I think...
> right?
> I'm also pretty sure there are RIPE Atlas measurements of 8.8.8.8/8.8.4.4
> that could tell you from which source-asn a backend sees traffic from..
> right? (or with a tiny bit of thought one could be proposed/executed)
>
>
> > There are
> > IPv4 Networks: 68
> > IPv6 Networks: 20
> > DNS Cluster’s Identified by POP Code’s: 20
> >
> > DNS Clusters identified by POP Code to City, State, or Country. Not all
> of
> > these are Google’s Core Datacenters, some of them are Edge Points of
> > 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          Washington, DC
> > syd        Sydney, Australia
> > lhr          London, UK
> > mrn        Lenoir, NC
> > tpe        Taiwan
> > atl          Altanta, GA
> > tul          Tulsa, OK
> > lpp          Findland
> > bru        Brussels, Belgium
> > cbf        Council Bluffs, IA
> > chs        Charleston, SC
> > dls          The Dalles, Oregon
> > dub        Dublin, Ireland
> > sin          Singapore
> > fra          Frankfort, Germany
> > bom      Mumbai, India
> > gru        Sao Paulo, Brazil
> > scl          Santiago, Chile
> > nrt          Tokyo, Japan
> > grq        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"                    <<<<<<DNS Server IP, reference the
> > list above to get the cluster, Council Bluffs, IA
> > "edns0-client-subnet 207.xxx.xxx.0/24"
> > <<<< Your Source IP Block
> >
> >
> > Side note, the google dns servers will not respond to DNS queries to the
> > Cluster’s Member’s 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
> > cluster member ip’s 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.
> >
> >
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