DNS/TCP/facebook.com/a.ns.c10r.facebook.com/2について、ここに記述してください。
$ dig z-p42-instagram.c10r.facebook.com @a.ns.c10r.facebook.com ; <<>> DiG 9.12.1 <<>> z-p42-instagram.c10r.facebook.com @a.ns.c10r.facebook.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 30762 ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 5 ;; WARNING: recursion requested but not available ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 512 ;; QUESTION SECTION: ;z-p42-instagram.c10r.facebook.com. IN A ;; ANSWER SECTION: z-p42-instagram.c10r.facebook.com. 60 IN A 31.13.82.174 ;; AUTHORITY SECTION: c10r.facebook.com. 3600 IN NS a.ns.c10r.facebook.com. c10r.facebook.com. 3600 IN NS b.ns.c10r.facebook.com. ;; ADDITIONAL SECTION: a.ns.c10r.facebook.com. 3600 IN AAAA 2a03:2880:fffe:b:face:b00c:0:99 a.ns.c10r.facebook.com. 3600 IN A 69.171.239.11 b.ns.c10r.facebook.com. 3600 IN AAAA 2a03:2880:ffff:b:face:b00c:0:99 b.ns.c10r.facebook.com. 3600 IN A 69.171.255.11 ;; Query time: 36 msec ;; SERVER: 69.171.239.11#53(69.171.239.11) ;; WHEN: Sun Apr 22 14:52:27 JST 2018 ;; MSG SIZE rcvd: 201
1. TCP 指定
tmaeno@u16:~$ dig +tcp z-p42-instagram.c10r.facebook.com @a.ns.c10r.facebook.com ;; Connection to 69.171.239.11#53(69.171.239.11) for z-p42-instagram.c10r.facebook.com failed: connection refused. ;; Connection to 2a03:2880:fffe:b:face:b00c:0:99#53(2a03:2880:fffe:b:face:b00c:0:99) for z-p42-instagram.c10r.facebook.com failed: network unreachable.