watchNS/iana-servers.netについて、ここに記述してください。
$ dig -t ns iana-servers.net
; <<>> DiG 9.9.5-3ubuntu0.7-Ubuntu <<>> -t ns iana-servers.net ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4520 ;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 1220 ;; QUESTION SECTION: ;iana-servers.net. IN NS ;; ANSWER SECTION: iana-servers.net. 1800 IN NS b.iana-servers.net. iana-servers.net. 1800 IN NS a.iana-servers.net. iana-servers.net. 1800 IN NS ns.icann.org. iana-servers.net. 1800 IN NS c.iana-servers.net. ;; Query time: 187 msec ;; SERVER: 127.0.0.2#53(127.0.0.2) ;; WHEN: Fri Feb 12 20:52:36 JST 2016 ;; MSG SIZE rcvd: 119