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

Thu Aug 24 00:39:27 UTC 2017

On Wed, Aug 23, 2017 at 8:30 PM, Joe Hamelin <joe at nethead.com> wrote:

> Gee Chris, that's kind of an asinine response.  Erik took the time to let
> us know about what he had found out, with
>

sure, except I think the link has even been posted to nanog in the past.
My point was really: it's documented, so you don't have to do the work.

-chris

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 <(360)%20474-7474>
>
> 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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