while debugging some weird Cisco telephony server issue we discovered the following behaviour:
pdns-recursor on current debian-stable:
dig smartreceiver.cisco.com AAAA
; <<>> DiG 9.16.33-Debian <<>> smartreceiver.cisco.com AAAA
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 40517
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;smartreceiver.cisco.com. IN AAAA
;; ANSWER SECTION:
smartreceiver.cisco.com. 616 IN CNAME smartreceiver.xglb.cisco.com.
;; Query time: 1808 msec
;; SERVER: 172.17.113.53#53(172.17.113.53)
;; WHEN: Fri Nov 18 12:18:20 CET 2022
;; MSG SIZE rcvd: 85
wheras unbound on current debian-stable gives:
dig smartreceiver.cisco.com AAAA @172.17.113.54
; <<>> DiG 9.16.33-Debian <<>> smartreceiver.cisco.com AAAA @172.17.113.54
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19342
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;smartreceiver.cisco.com. IN AAAA
;; ANSWER SECTION:
smartreceiver.cisco.com. 1797 IN CNAME smartreceiver.xglb.cisco.com.
;; Query time: 3008 msec
;; SERVER: 172.17.113.54#53(172.17.113.54)
;; WHEN: Fri Nov 18 12:22:05 CET 2022
;; MSG SIZE rcvd: 85
google-dns:
dig smartreceiver.cisco.com AAAA @8.8.8.8
; <<>> DiG 9.16.33-Debian <<>> smartreceiver.cisco.com AAAA @8.8.8.8
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28403
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;smartreceiver.cisco.com. IN AAAA
;; ANSWER SECTION:
smartreceiver.cisco.com. 1686 IN CNAME smartreceiver.xglb.cisco.com.
;; Query time: 148 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Fri Nov 18 12:22:45 CET 2022
;; MSG SIZE rcvd: 85
In Wireshark, we could observe, that the actual response to the AAAA query is empty, yet unbound and google-dns deliver information that enables the client to proceed. Is this by design or am I just missing the correct option in the settings file?
