1. watchA
2. おかしな返答
ns0.sfcは hcのNSでもあるから。
$ dig -t soa hc.keio.ac.jp @ns0.sfc.keio.ac.jp ; <<>> DiG 9.11.3-1ubuntu1.11-Ubuntu <<>> -t soa hc.keio.ac.jp @ns0.sfc.keio.ac.jp ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39849 ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 6, ADDITIONAL: 11 ;; WARNING: recursion requested but not available ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ; COOKIE: 3be00e878f16f4a37b00c6b95ef3e94e8b152455ace1c9fe (good) ;; QUESTION SECTION: ;hc.keio.ac.jp. IN SOA ;; ANSWER SECTION: hc.keio.ac.jp. 86400 IN SOA nsm0.keio.ac.jp. postmaster.keio.ac.jp. 2020040800 10800 3600 1209600 3600 ;; AUTHORITY SECTION: hc.keio.ac.jp. 86400 IN NS ns.st.keio.ac.jp. hc.keio.ac.jp. 86400 IN NS kogwy.cc.keio.ac.jp. hc.keio.ac.jp. 86400 IN NS ns.hc.keio.ac.jp. hc.keio.ac.jp. 86400 IN NS ns.sc.keio.ac.jp. hc.keio.ac.jp. 86400 IN NS ns0.sfc.keio.ac.jp. hc.keio.ac.jp. 86400 IN NS ns.mita.keio.ac.jp. ;; ADDITIONAL SECTION: ns.hc.keio.ac.jp. 86400 IN A 131.113.224.8 ns.st.keio.ac.jp. 3600 IN A 131.113.1.8 ns.mita.keio.ac.jp. 86400 IN A 131.113.192.8 ns0.sfc.keio.ac.jp. 3600 IN A 133.27.4.121 kogwy.cc.keio.ac.jp. 3600 IN A 131.113.1.1 ns.hc.keio.ac.jp. 86400 IN AAAA 2001:df0:eb:4259::8 ns.st.keio.ac.jp. 3600 IN AAAA 2001:df0:eb:8001::8 ns.mita.keio.ac.jp. 86400 IN AAAA 2001:df0:eb:2106::8 ns0.sfc.keio.ac.jp. 3600 IN AAAA 2001:df2:c900:1100::4:121 kogwy.cc.keio.ac.jp. 3600 IN AAAA 2001:df0:eb:8001::1 ;; Query time: 20 msec ;; SERVER: 133.27.4.121#53(133.27.4.121) ;; WHEN: Thu Jun 25 09:01:18 JST 2020 ;; MSG SIZE rcvd: 466