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

Thu Aug 24 02:40:12 UTC 2017

Excellent, thanks for sharing.

El 23/8/17 a las 4:09 p.m., Erik Sundberg escribió:
> 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
>
> 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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