jueves, 24 de agosto de 2017

Google DNS --- Averiguando cual Cluster estas utilizando

(this is -almost- a copy / paste of an email sent by Erik Sundberg to nanog mailing list on 
August 23). 
This post is being posted with his explicit permission.

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 
Anycast routes your DNS queries to the closes DNS cluster based on the 
best route / 
lowest metric to   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. @

How to print this list in a table format. 
Script from: https://developers.google.com/speed/public-dns/faq
for LOC in $(dig -t TXT +short locations.publicdns.goog. @
  case $LOC in
    '') : ;;
    *.*|*:*) printf '%s ' ${LOC} ;;
    *) printf '%s\n' ${LOC} ;;

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. iad iad syd lhr mrn tpe atl mrn tul lpp bru cbf bru lpp chs cbf chs lpp dls dub mrn cbf lpp cbf tul mrn atl cbf bru cbf cbf chs dls dls sin tul lhr lhr sin syd syd fra fra fra bom bom gru atl gru cbf scl tpe cbf tul chs lpp tul mrn tul atl cbf nrt nrt nrt iad grq grq 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 

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 @
""                     <<<<<dig o-o.myaddr.l.google.com -t 
txt +short @
"" "" "" "" "" 
"" Which all are Google DNS Networks in Atlanta. atl atl atl atl 2607:f8b0:4002::/48 atl

 Just thought it would be helpful when troubleshooting google DNS issues.

(one more time: this is -almost- a copy / paste of an email sent by Erik Sundberg to nanog mailing 
list on August 23). This post is being posted with his explicit permission.

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