How shall I understand the output of dig?
A DNS server stores a database of resource records.
Does dig return the resource records in the database of some DNS server? If yes, which DNS server's database's resource records does dig return?
For example, dig doesn't seem to return the resource records in the database of DNS server a.edu-servers.net.
$ dig @a.edu-servers.net robot.cs.washington.edu ; <<>> DiG 9.11.3-1ubuntu1.3-Ubuntu <<>> @a.edu-servers.net robot.cs.washington.edu ; (2 servers found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2401 ;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 7 ;; WARNING: recursion requested but not available ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;robot.cs.washington.edu. IN A ;; AUTHORITY SECTION: washington.edu. 172800 IN NS marge.cac.washington.edu. washington.edu. 172800 IN NS hanna.cac.washington.edu. washington.edu. 172800 IN NS holly.s.uw.edu. ;; ADDITIONAL SECTION: marge.cac.washington.edu. 172800 IN A 140.142.5.13 marge.cac.washington.edu. 172800 IN AAAA 2607:4000:200:43::13 hanna.cac.washington.edu. 172800 IN A 140.142.5.5 hanna.cac.washington.edu. 172800 IN AAAA 2607:4000:200:42::5 holly.s.uw.edu. 172800 IN A 173.250.227.69 holly.s.uw.edu. 172800 IN AAAA 2607:4000:301:1::69 ;; Query time: 46 msec ;; SERVER: 192.5.6.30#53(192.5.6.30) ;; WHEN: Mon Feb 11 16:27:09 EST 2019 ;; MSG SIZE rcvd: 253