I'm using nslookup and trying to figure out the difference in authoritative and non-authoritative responses. These two responses seem to be consistent (they give the same answer if you run the command multiple times).
Normal nslookup call
$ nslookup google.com
Server: 192.168.1.1
Address: 192.168.1.1#53
Non-authoritative answer:
Name: google.com
Address: 72.14.213.104
Name: google.com
Address: 72.14.213.105
Name: google.com
Address: 72.14.213.106
Name: google.com
Address: 72.14.213.147
Name: google.com
Address: 72.14.213.99
Name: google.com
Address: 72.14.213.103
Nslookup using google's authoritative server
$ nslookup google.com ns1.google.com
Server: ns1.google.com
Address: 216.239.32.10#53
Name: google.com
Address: 74.125.225.19
Name: google.com
Address: 74.125.225.20
Name: google.com
Address: 74.125.225.16
Name: google.com
Address: 74.125.225.17
Name: google.com
Address: 74.125.225.18
Any idea why these are different? Should these be giving different responses?
When I ping google.com, it shows 72.14.213.104 and the RTT is 1/3 of the RTT for pinging 74.125.225.19.
Can anyone explain this?