ccTLD/atについて、ここに記述してください。

%dnsq ns at a.root-servers.net 

2 at:
463 bytes, 1+0+8+14 records, response, noerror
query: 2 at
authority: at 172800 NS d.ns.at
authority: at 172800 NS j.ns.at
authority: at 172800 NS n.ns.at
authority: at 172800 NS r.ns.at
authority: at 172800 NS u.ns.at
authority: at 172800 NS ns1.univie.ac.at
authority: at 172800 NS ns2.univie.ac.at
authority: at 172800 NS ns9.univie.ac.at
additional: d.ns.at 172800 A 81.91.161.98
additional: j.ns.at 172800 A 194.146.106.50
additional: n.ns.at 172800 A 81.91.173.130
additional: r.ns.at 172800 A 194.0.25.10
additional: u.ns.at 172800 A 195.66.241.82
additional: ns1.univie.ac.at 172800 A 78.104.144.2
additional: ns2.univie.ac.at 172800 A 192.92.125.2
additional: ns9.univie.ac.at 172800 A 194.0.10.100
additional: d.ns.at 172800 28 *\002\005h\000\040\000\001\000\000\000\000\000\000\000\015
additional: j.ns.at 172800 28 \040\001\006|\020\020\000\022\000\000\000\000\000\000\000S
additional: r.ns.at 172800 28 \040\001\006x\000\040\000\000\000\000\000\000\000\000\000\020
additional: ns1.univie.ac.at 172800 28 \040\001\006(\0400C\001\000\000\000\000\000\000\000\002
additional: ns2.univie.ac.at 172800 28 \040\001\006x\000\034\000\000\000\000\000\000\000\000\000\002
additional: ns9.univie.ac.at 172800 28 \040\001\006x\000\015\000\000\000\000\000\000\000\000\312\376

%dnsq ns at j.ns.at 

2 at:
359 bytes, 1+8+0+9 records, response, authoritative, noerror
query: 2 at
answer: at 172800 NS ns1.univie.ac.at
answer: at 172800 NS ns2.univie.ac.at
answer: at 172800 NS n.ns.at
answer: at 172800 NS j.ns.at
answer: at 172800 NS ns9.univie.ac.at
answer: at 172800 NS d.ns.at
answer: at 172800 NS r.ns.at
answer: at 172800 NS u.ns.at
additional: d.ns.at 172800 A 81.91.161.98
additional: d.ns.at 172800 28 *\002\005h\000\040\000\001\000\000\000\000\000\000\000\015
additional: j.ns.at 172800 A 194.146.106.50
additional: j.ns.at 172800 28 \040\001\006|\020\020\000\022\000\000\000\000\000\000\000S
additional: n.ns.at 172800 A 81.91.173.130
additional: n.ns.at 172800 28 *\002\005h\002\201\000\000\000\000\000\000\000\000\0010
additional: r.ns.at 172800 A 194.0.25.10
additional: r.ns.at 172800 28 \040\001\006x\000\040\000\000\000\000\000\000\000\000\000\020
additional: u.ns.at 172800 A 195.66.241.82

1. ns.at ドメインはない

%dnsq ns ns.at j.ns.at 

2 ns.at:
90 bytes, 1+0+1+0 records, response, authoritative, noerror
query: 2 ns.at
authority: at 10800 SOA dns.nic.at domain-admin.univie.ac.at 1429095601 10800 3600 604800 10800

2. ac.at は同居

%dnsq ns ac.at j.ns.at 

2 ac.at:
277 bytes, 1+0+4+8 records, response, noerror
query: 2 ac.at
authority: ac.at 10800 NS n.ns.at
authority: ac.at 10800 NS ns2.univie.ac.at
authority: ac.at 10800 NS d.ns.at
authority: ac.at 10800 NS ns1.univie.ac.at
additional: d.ns.at 172800 A 81.91.161.98
additional: d.ns.at 172800 28 *\002\005h\000\040\000\001\000\000\000\000\000\000\000\015
additional: n.ns.at 172800 A 81.91.173.130
additional: n.ns.at 172800 28 *\002\005h\002\201\000\000\000\000\000\000\000\000\0010
additional: ns1.univie.ac.at 10800 A 78.104.144.2
additional: ns1.univie.ac.at 10800 28 \040\001\006(\0400C\001\000\000\000\000\000\000\000\002
additional: ns2.univie.ac.at 10800 A 192.92.125.2
additional: ns2.univie.ac.at 10800 28 \040\001\006x\000\034\000\000\000\000\000\000\000\000\000\002