[dns-operations] about answer status

[Kevin C.]

Hello,

Sometime I got "NOERROR" from the answer, but sometime got "NXDOMAIN".
At what case the nameserver returns "NOERROR" or "NXDOMAIN" for a 
non-exist record? Thank you.

There are two digs below, please notice they are different hostnames.

$ dig defensor.game.yy.com @localhost

; <<>> DiG 9.6.1-P2 <<>> defensor.game.yy.com @localhost
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35846
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;defensor.game.yy.com.          IN      A

;; AUTHORITY SECTION:
game.yy.com.            600     IN      SOA     dwdns1.nsbeta.info. 
support.dnsbed.com. 150907 10800 3600 604800 600

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Mon Jun  8 16:07:14 2015
;; MSG SIZE  rcvd: 107


$ dig defenser.game.yy.com @localhost

; <<>> DiG 9.6.1-P2 <<>> defenser.game.yy.com @localhost
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 17567
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;defenser.game.yy.com.          IN      A

;; AUTHORITY SECTION:
game.yy.com.            600     IN      SOA     dwdns1.nsbeta.info. 
support.dnsbed.com. 150907 10800 3600 604800 600

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Mon Jun  8 16:07:42 2015
;; MSG SIZE  rcvd: 107