[dns-operations] RFC7816 - do not remove

[T.Suzuki]

What's this? :-)

~% drill txt elb.amazonaws.com @r1.amazonaws.com
;; ->>HEADER<<- opcode: QUERY, rcode: NOERROR, id: 4102
;; flags: qr aa rd ; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4 
;; QUESTION SECTION:
;; elb.amazonaws.com.	IN	TXT

;; ANSWER SECTION:
elb.amazonaws.com.	300	IN	TXT	"RFC7816 - do not remove"

;; AUTHORITY SECTION:
amazonaws.com.	3600	IN	NS	r1.amazonaws.com.
amazonaws.com.	3600	IN	NS	r2.amazonaws.com.
amazonaws.com.	3600	IN	NS	u1.amazonaws.com.
amazonaws.com.	3600	IN	NS	u2.amazonaws.com.

;; ADDITIONAL SECTION:
r1.amazonaws.com.	7211	IN	A	205.251.192.27
r2.amazonaws.com.	7213	IN	A	205.251.195.199
u1.amazonaws.com.	1800	IN	A	156.154.64.10
u2.amazonaws.com.	1800	IN	A	156.154.65.10

;; Query time: 178 msec
;; SERVER: 64:ff9b::cdfb:c01b
;; WHEN: Mon Dec 18 17:06:07 2017
;; MSG SIZE  rcvd: 203

I remember that this ENT returned NXDOMAIN.

~% dig elb.amazonaws.com @r1.amazonaws.com
 
; <<>> DiG 9.9.5 <<>> elb.amazonaws.com @r1.amazonaws.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 10800
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;elb.amazonaws.com.	IN A

;; AUTHORITY SECTION:
amazonaws.com.		3593 IN	SOA dns-external-master.amazon.com. hostmaster.amazon.com. (
				2012708585 ; serial
				180        ; refresh (3 minutes)
				60         ; retry (1 minute)
				2592000    ; expire (4 weeks 2 days)
				3593       ; minimum (59 minutes 53 seconds)
				)

;; Query time: 262 msec
;; SERVER: 205.251.192.27#53(205.251.192.27)
;; WHEN: Thu Oct 05 13:00:52 JST 2017
;; MSG SIZE  rcvd: 120

~% dig elb.amazonaws.com @u1.amazonaws.com

; <<>> DiG 9.9.5 <<>> elb.amazonaws.com @u1.amazonaws.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 64248
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65235
;; QUESTION SECTION:
;elb.amazonaws.com.	IN A

;; AUTHORITY SECTION:
amazonaws.com.		3593 IN	SOA pdns1.ultradns.net. hostmaster.amazon.com. (
				2014061348 ; serial
				180        ; refresh (3 minutes)
				60         ; retry (1 minute)
				2592000    ; expire (4 weeks 2 days)
				3593       ; minimum (59 minutes 53 seconds)
				)

;; Query time: 19 msec
;; SERVER: 156.154.64.10#53(156.154.64.10)
;; WHEN: Thu Oct 05 13:00:56 JST 2017
;; MSG SIZE  rcvd: 11

-- 
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T.Suzuki