domain name system - Order in which Resource Records(RR) are answered by Bind if Order and preference are Same

I had a query on how the following Records can be ordered on how the Records are configured in the Zone file

I have done 2 different Tests

I have configured following records in the Zone file e164enum.net with TTL value as 0

2.7.5.2.7.9.2.5.3.1.8.e164enum.net. IN NAPTR 100 10 "u" "E2U+sip" "!^.*$!sip:7895673454@ATLANTA.COM;user=phone!" .
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. IN NAPTR 100 10 "u" "E2U+sip" "!^.*$!sip:7895673453@ATLANTA.COM;user=phone!" .

Now whenever I run a "dig" query on the bind server for "dig 2.7.5.2.7.9.2.5.3.1.8.e164enum.net. NAPTR"

I receive responses like, toggled in Answer section

First dig query

;; <<>> DiG 9.9.5-rpz2+rl.14038.05-P1 <<>> 2.7.5.2.7.9.2.5.3.1.8.e164enum.net. NAPTR
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37270
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 2

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;2.7.5.2.7.9.2.5.3.1.8.e164enum.net. IN NAPTR


;; ANSWER SECTION:
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. 0 IN NAPTR  100 10 "u" "E2U+sip" "!^.*$!sip:7895673453@ATLANTA.COM\;user=phone!" .
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. 0 IN NAPTR  100 10 "u" "E2U+sip" "!^.*$!sip:7895673454@ATLANTA.COM\;user=phone!" .

;; AUTHORITY SECTION:
e164enum.net.           0       IN      NS      HP3bl10VM5DNS.e164enum.net.

;; ADDITIONAL SECTION:
HP3bl10VM5DNS.e164enum.net. 0   IN      A       10.54.212.235


;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Tue Jul 19 00:31:16 IST 2016
;; MSG SIZE  rcvd: 261

2nd dig query

; <<>> DiG 9.9.5-rpz2+rl.14038.05-P1 <<>> 2.7.5.2.7.9.2.5.3.1.8.e164enum.net. NAPTR

;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40073
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 2

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;2.7.5.2.7.9.2.5.3.1.8.e164enum.net. IN NAPTR


;; ANSWER SECTION:
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. 0 IN NAPTR  100 10 "u" "E2U+sip" "!^.*$!sip:7895673454@ATLANTA.COM\;user=phone!" .
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. 0 IN NAPTR  100 10 "u" "E2U+sip" "!^.*$!sip:7895673453@ATLANTA.COM\;user=phone!" .

;; AUTHORITY SECTION:
e164enum.net.           0       IN      NS      HP3bl10VM5DNS.e164enum.net.

;; ADDITIONAL SECTION:
HP3bl10VM5DNS.e164enum.net. 0   IN      A       10.54.212.235


;; Query time: 1 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Tue Jul 19 00:31:19 IST 2016
;; MSG SIZE  rcvd: 261

As I see, the responses (RR Answers) from bind server toggle for each dig

Since I did not want the Answers to be toggled in each susbsequent digs, and I wanted the Answers to be in the same Order they were configured in the Zone file(since the Order and Preference of both these records were same), I enabled this line in the options field of named.conf

rrset-order {order fixed;};

and restarted named

I ran the dig query again
This time, the Answers did not toggle, but I found that, the second configured RR was being Answered as first always
This record was always being answered first inspite of being second in my configured preference(assuming that configuring rrset-order will always return RR Answers in the same order as configured in the Zone file)

Query#1

; <<>> DiG 9.9.5-rpz2+rl.14038.05-P1 <<>> 2.7.5.2.7.9.2.5.3.1.8.e164enum.net. NAPTR
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18221
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 2

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:

;2.7.5.2.7.9.2.5.3.1.8.e164enum.net. IN NAPTR

;; ANSWER SECTION:
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. 0 IN NAPTR  100 10 "u" "E2U+sip" "!^.*$!sip:7895673453@ATLANTA.COM\;user=phone!" .
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. 0 IN NAPTR  100 10 "u" "E2U+sip" "!^.*$!sip:7895673454@ATLANTA.COM\;user=phone!" .

;; AUTHORITY SECTION:
e164enum.net.           0       IN      NS      HP3bl10VM5DNS.e164enum.net.

;; ADDITIONAL SECTION:

HP3bl10VM5DNS.e164enum.net. 0   IN      A       10.54.212.235

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Tue Jul 19 00:36:30 IST 2016
;; MSG SIZE  rcvd: 261

Query#2

; <<>> DiG 9.9.5-rpz2+rl.14038.05-P1 <<>> 2.7.5.2.7.9.2.5.3.1.8.e164enum.net. NAPTR
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17082
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 2

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;2.7.5.2.7.9.2.5.3.1.8.e164enum.net. IN NAPTR


;; ANSWER SECTION:
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. 0 IN NAPTR  100 10 "u" "E2U+sip" "!^.*$!sip:7895673453@ATLANTA.COM\;user=phone!" .
2.7.5.2.7.9.2.5.3.1.8.e164enum.net. 0 IN NAPTR  100 10 "u" "E2U+sip" "!^.*$!sip:7895673454@ATLANTA.COM\;user=phone!" .

;; AUTHORITY SECTION:
e164enum.net.           0       IN      NS      HP3bl10VM5DNS.e164enum.net.

;; ADDITIONAL SECTION:
HP3bl10VM5DNS.e164enum.net. 0   IN      A       10.54.212.235


;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Tue Jul 19 00:36:33 IST 2016
;; MSG SIZE  rcvd: 261

Why is Bind answering the Second RR as first and not my original First RR as 1st Answer?

Answer

The bind documentation says (for my bind version 9.9.5) :

In this release of BIND 9, the rrset-order statement does not support "fixed" ordering by default. Fixed ordering can be enabled at compile time by specifying "--enable-fixed-rrset" on
the "configure" command line.

So maybe the problem is in your bind version. You did not specify which one you are using, maybe you should try with another version?