1. watchA

akam.net からの返事には 真のglue と余計なA/AAAAが混在している。(sibling domain glueと呼ばれている。)

$ dig -t ns cc.keio.ac.jp @a4-65.akam.net.

; <<>> DiG 9.11.3-1ubuntu1.11-Ubuntu <<>> -t ns cc.keio.ac.jp @a4-65.akam.net.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4990
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 6, ADDITIONAL: 13
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;cc.keio.ac.jp.                 IN      NS

;; AUTHORITY SECTION:
cc.keio.ac.jp.          10800   IN      NS      ns0.sfc.keio.ac.jp.
cc.keio.ac.jp.          10800   IN      NS      kogwy.cc.keio.ac.jp.
cc.keio.ac.jp.          10800   IN      NS      ns.st.keio.ac.jp.
cc.keio.ac.jp.          10800   IN      NS      ns.mita.keio.ac.jp.
cc.keio.ac.jp.          10800   IN      NS      ns.hc.keio.ac.jp.
cc.keio.ac.jp.          10800   IN      NS      ns.sc.keio.ac.jp.

;; ADDITIONAL SECTION:
ns.mita.keio.ac.jp.     10800   IN      AAAA    2001:df0:eb:2106::8
ns.st.keio.ac.jp.       10800   IN      A       131.113.1.8
kogwy.cc.keio.ac.jp.    10800   IN      AAAA    2001:df0:eb:8001::1
ns.mita.keio.ac.jp.     10800   IN      A       131.113.192.8
ns.hc.keio.ac.jp.       10800   IN      A       131.113.224.8
ns.hc.keio.ac.jp.       10800   IN      AAAA    2001:df0:eb:4259::8
ns0.sfc.keio.ac.jp.     10800   IN      AAAA    2001:200:1c0:1100::121
ns.sc.keio.ac.jp.       10800   IN      A       131.113.191.8
ns.st.keio.ac.jp.       10800   IN      AAAA    2001:df0:eb:8001::8
ns0.sfc.keio.ac.jp.     10800   IN      A       133.27.4.121
ns.sc.keio.ac.jp.       10800   IN      AAAA    2001:df0:eb:612d::191:8
kogwy.cc.keio.ac.jp.    10800   IN      A       131.113.1.1

;; Query time: 23 msec
;; SERVER: 72.246.46.65#53(72.246.46.65)
;; WHEN: Thu Jun 25 08:41:06 JST 2020
;; MSG SIZE  rcvd: 430

2. kogwy

余計なものはついていない。

• kogwy.cc.keio.ac.jp. 3600 IN A 131.113.1.1

$ dig -t ns cc.keio.ac.jp @kogwy.cc.keio.ac.jp.

; <<>> DiG 9.11.3-1ubuntu1.11-Ubuntu <<>> -t ns cc.keio.ac.jp @kogwy.cc.keio.ac.jp.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20448
;; flags: qr aa rd; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;cc.keio.ac.jp.                 IN      NS

;; ANSWER SECTION:
cc.keio.ac.jp.          3600    IN      NS      ns.mita.keio.ac.jp.
cc.keio.ac.jp.          3600    IN      NS      ns.hc.keio.ac.jp.
cc.keio.ac.jp.          3600    IN      NS      kogwy.cc.keio.ac.jp.
cc.keio.ac.jp.          3600    IN      NS      ns0.sfc.keio.ac.jp.
cc.keio.ac.jp.          3600    IN      NS      ns.sc.keio.ac.jp.
cc.keio.ac.jp.          3600    IN      NS      ns.st.keio.ac.jp.

;; Query time: 18 msec
;; SERVER: 131.113.1.1#53(131.113.1.1)
;; WHEN: Thu Jun 25 08:46:00 JST 2020
;; MSG SIZE  rcvd: 166

3. しかし

これはkogwy.cc が cc, hc, mita, sc, sfc, st のゾーンを持つからである。(keio.ac.jp ゾーンも)

$ dig -t a ns.mita.keio.ac.jp @kogwy.cc.keio.ac.jp.

; <<>> DiG 9.11.3-1ubuntu1.11-Ubuntu <<>> -t a ns.mita.keio.ac.jp @kogwy.cc.keio.ac.jp.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36951
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;ns.mita.keio.ac.jp.            IN      A

;; ANSWER SECTION:
ns.mita.keio.ac.jp.     86400   IN      A       131.113.192.8

;; Query time: 19 msec
;; SERVER: 131.113.1.1#53(131.113.1.1)
;; WHEN: Thu Jun 25 08:49:00 JST 2020
;; MSG SIZE  rcvd: 63

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