NXDOMAIN for an ENT (Empty Non-Terminal)
dig @ns1.flexbalancer.net. A a7e454.flexbalancer.net
; <<>> DiG 9.10.3-P4-Debian <<>> @ns1.flexbalancer.net. A a7e454.flexbalancer.net
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 627
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 512
;; QUESTION SECTION:
;a7e454.flexbalancer.net. IN A
;; Query time: 20 msec
;; SERVER: 2400:cb00:2049:1::a29f:18a3#53(2400:cb00:2049:1::a29f:18a3)
;; WHEN: Wed Jul 31 12:16:34 CEST 2019
;; MSG SIZE rcvd: 52
% dig @ns1.flexbalancer.net. A jsdelivr.a7e454.flexbalancer.net
; <<>> DiG 9.10.3-P4-Debian <<>> @ns1.flexbalancer.net. A jsdelivr.a7e454.flexbalancer.net
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17070
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 512
;; QUESTION SECTION:
;jsdelivr.a7e454.flexbalancer.net. IN A
;; ANSWER SECTION:
jsdelivr.a7e454.flexbalancer.net. 10 IN CNAME dualstack.f3.shared.global.fastly.net.
;; Query time: 20 msec
;; SERVER: 2400:cb00:2049:1::a29f:18a3#53(2400:cb00:2049:1::a29f:18a3)
;; WHEN: Wed Jul 31 12:17:37 CEST 2019
;; MSG SIZE rcvd: 109