Open DNS resolution

593 views
Skip to first unread message

anupna...@gmail.com

unread,
Feb 22, 2016, 1:09:19 PM2/22/16
to public-dns-discuss, thvel...@gmail.com, pavan...@gmail.com
My local DNS resolve with the following IP for the portal.azure.com.

C:\Users\anupnam>nslookup  portal.azure.com
Server:  FTTX.Gateway
Address:  192.168.0.1
Non-authoritative answer:
Name:    onecloudshell-prod-bm-02.cloudapp.net
Address:  104.211.160.130
Aliases:  portal.azure.com
          portal.azure.com.trafficmanager.net

But if I use open DNS from the same source machine I get the following resolution:

C:\Users\anupnam>nslookup  portal.azure.com  8.8.8.8
Server:  google-public-dns-a.google.com
Address:  8.8.8.8
Non-authoritative answer:
Name:    onecloudshell-prod-sg-02.cloudapp.net
Address:  104.215.159.8
Aliases:  portal.azure.com
          portal.azure.com.trafficmanager.net


I am trying to understand how does open DNS does recursive query against the authoritative DNS servers. In case if I am using 8.8.8.8 IP as DNS from India which IP will be seen on the authoritative DNS servers for DNS query.



Shen Wan

unread,
Feb 23, 2016, 9:04:23 AM2/23/16
to public-dns-discuss, thvel...@gmail.com, pavan...@gmail.com, anupna...@gmail.com
First, our name is "Google Public DNS", not "Open DNS" :)
You may run: dig +short @8.8.8.8 o-o.myaddr.l.google.com txt
or: nslookup -type=TXT o-o.myaddr.l.google.com 8.8.8.8

It will show your IP address and the ECS option 8.8.8.8 sees when you make DNS queries.

anup namdhari

unread,
Feb 23, 2016, 10:46:41 AM2/23/16
to Shen Wan, public-dns-discuss, thvel...@gmail.com, pavan...@gmail.com
Thanks Shen, I get the following answer. How would I know the following IP belongs which region and on which region request is getting hit.

C:\Users\anupnam>nslookup -type=TXT o-o.myaddr.l.google.com 8.8.8.8
Address:  8.8.8.8

Non-authoritative answer:

        "74.125.190.148"

        "edns0-client-subnet 203.127.159.129/32"


Shen Wan

unread,
Feb 23, 2016, 12:44:27 PM2/23/16
to anup namdhari, public-dns-discuss, thvel...@gmail.com, pavan...@gmail.com
In this case 74.125.190.148 is the resolver's IP address as seen by ns?.google.com.
And 203.127.159.129 is the IP address that Google Public DNS passed to ns?.google.com to geo-locate your DNS request. It is in Singapore.

Alexander Dupuy

unread,
Feb 23, 2016, 5:15:30 PM2/23/16
to Shen Wan, anup namdhari, public-dns-discuss, thvel...@gmail.com, pavan...@gmail.com
Note that Azure cloud portal authoritative DNS does not support EDNS Client Subnet at the current time; it geo-locates based on the IP address that sends the query. So Azure will geo-locate any client using Google Public DNS at the nearest (by anycast distance) Google datacenter where the resolver sends queries to the authoritative DNS servers (you can see the entire list at https://developers.google.com/speed/public-dns/faq#locations).

In your case, this will be Singapore; until Azure supported EDNS Client Subnet; there is little we can do to improve this situation, short of opening a Google datacenter in your country.
Reply all
Reply to author
Forward
0 new messages