% dig +noall +answer heroku.com
heroku.com. 30 IN A 50.19.85.156
heroku.com. 30 IN A 50.19.85.154
heroku.com. 30 IN A 50.19.85.132
% dig -x 50.19.85.156 +noall +answer
; <<>> DiG 9.8.3-P1 <<>> -x 50.19.85.156 +noall +answer
;; global options: +cmd
156.85.19.50.in-addr.arpa. 263 IN PTR ec2-50-19-85-156.compute-1.amazonaws.com.
% dig heroku.com
; <<>> DiG 9.8.3-P1 <<>> heroku.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16922
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 8, ADDITIONAL: 8
;; QUESTION SECTION:
;heroku.com. IN A
;; ANSWER SECTION:
heroku.com. 30 IN A 50.19.85.156
heroku.com. 30 IN A 50.19.85.132
heroku.com. 30 IN A 50.19.85.154
;; AUTHORITY SECTION:
heroku.com. 58802 IN NS ns-1253.awsdns-28.org.
heroku.com. 58802 IN NS ns3.p19.dynect.net.
heroku.com. 58802 IN NS ns1.p19.dynect.net.
heroku.com. 58802 IN NS ns2.p19.dynect.net.
heroku.com. 58802 IN NS ns4.p19.dynect.net.
heroku.com. 58802 IN NS ns-405.awsdns-50.com.
heroku.com. 58802 IN NS ns-1538.awsdns-00.co.uk.
heroku.com. 58802 IN NS ns-975.awsdns-57.net.
;; ADDITIONAL SECTION:
ns1.p19.dynect.net. 83793 IN A 208.78.70.19
ns2.p19.dynect.net. 83636 IN A 204.13.250.19
ns3.p19.dynect.net. 83727 IN A 208.78.71.19
ns4.p19.dynect.net. 83727 IN A 204.13.251.19
ns-405.awsdns-50.com. 150222 IN A 205.251.193.149
ns-975.awsdns-57.net. 86304 IN A 205.251.195.207
ns-1253.awsdns-28.org. 83990 IN A 205.251.196.229
ns-1538.awsdns-00.co.uk. 83609 IN A 205.251.198.2
;; Query time: 34 msec
;; SERVER: 192.168.3.1#53(192.168.3.1)
;; WHEN: Thu Jan 5 16:54:39 2017
;; MSG SIZE rcvd: 424
Toggle tracing of the delegation path from the root name servers for the name being looked up.
% dig +trace heroku.com
; <<>> DiG 9.8.3-P1 <<>> +trace heroku.com
;; global options: +cmd
. 96903 IN NS g.root-servers.net.
. 96903 IN NS k.root-servers.net.
. 96903 IN NS l.root-servers.net.
. 96903 IN NS f.root-servers.net.
. 96903 IN NS j.root-servers.net.
. 96903 IN NS i.root-servers.net.
. 96903 IN NS d.root-servers.net.
. 96903 IN NS c.root-servers.net.
. 96903 IN NS a.root-servers.net.
. 96903 IN NS b.root-servers.net.
. 96903 IN NS m.root-servers.net.
. 96903 IN NS e.root-servers.net.
. 96903 IN NS h.root-servers.net.
;; Received 436 bytes from 192.168.3.1#53(192.168.3.1) in 95 ms
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
;; Received 488 bytes from 199.7.91.13#53(199.7.91.13) in 880 ms
heroku.com. 172800 IN NS ns1.p19.dynect.net.
heroku.com. 172800 IN NS ns3.p19.dynect.net.
heroku.com. 172800 IN NS ns2.p19.dynect.net.
heroku.com. 172800 IN NS ns4.p19.dynect.net.
heroku.com. 172800 IN NS ns-405.awsdns-50.com.
heroku.com. 172800 IN NS ns-975.awsdns-57.net.
heroku.com. 172800 IN NS ns-1538.awsdns-00.co.uk.
heroku.com. 172800 IN NS ns-1253.awsdns-28.org.
;; Received 344 bytes from 192.48.79.30#53(192.48.79.30) in 382 ms
heroku.com. 30 IN A 50.19.85.156
heroku.com. 30 IN A 50.19.85.132
heroku.com. 30 IN A 50.19.85.154
heroku.com. 86400 IN NS ns-1253.awsdns-28.org.
heroku.com. 86400 IN NS ns-1538.awsdns-00.co.uk.
heroku.com. 86400 IN NS ns-405.awsdns-50.com.
heroku.com. 86400 IN NS ns-975.awsdns-57.net.
heroku.com. 86400 IN NS ns1.p19.dynect.net.
heroku.com. 86400 IN NS ns2.p19.dynect.net.
heroku.com. 86400 IN NS ns3.p19.dynect.net.
heroku.com. 86400 IN NS ns4.p19.dynect.net.
;; Received 296 bytes from 205.251.196.229#53(205.251.196.229) in 35 ms
dig can connect to whatever resolver you want to via @. When there are any discrepancies, adding resolver would help.
dig domain @1.1.1.1 # Cloudflare
dig domain @8.8.8.8 # Google Public DNS
dig domain @208.67.220.220 # Cisco/OpenDNS