Em geral, os registros NS são armazenados como cola. Então, quando você vai para a.com
você vai para a raiz (* .root-servers.net) que são codificados em seus servidores dns. No caso de .com, você é apontado para * .gtld-servers.net, que hospeda o .com tld. De lá, você receberia os registros NS por a.com
, juntamente com os endereços IP, devido aos registros de cola. Aqui está um exemplo de procurar o google ..
[~] dig +trace google.com
; <<>> DiG 9.7.3 <<>> +trace google.com
;; global options: +cmd
. 321319 IN NS k.root-servers.net.
. 321319 IN NS c.root-servers.net.
. 321319 IN NS l.root-servers.net.
. 321319 IN NS g.root-servers.net.
. 321319 IN NS j.root-servers.net.
. 321319 IN NS f.root-servers.net.
. 321319 IN NS d.root-servers.net.
. 321319 IN NS h.root-servers.net.
. 321319 IN NS a.root-servers.net.
. 321319 IN NS m.root-servers.net.
. 321319 IN NS e.root-servers.net.
. 321319 IN NS b.root-servers.net.
. 321319 IN NS i.root-servers.net.
;; Received 512 bytes from 10.10.0.1#53(10.10.0.1) in 7 ms
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
;; Received 488 bytes from 192.5.5.241#53(f.root-servers.net) in 35 ms
google.com. 172800 IN NS ns2.google.com.
google.com. 172800 IN NS ns1.google.com.
google.com. 172800 IN NS ns3.google.com.
google.com. 172800 IN NS ns4.google.com.
;; Received 164 bytes from 192.26.92.30#53(c.gtld-servers.net) in 40 ms
google.com. 300 IN A 72.14.204.105
google.com. 300 IN A 72.14.204.103
google.com. 300 IN A 72.14.204.99
google.com. 300 IN A 72.14.204.147
google.com. 300 IN A 72.14.204.104
;; Received 108 bytes from 216.239.36.10#53(ns3.google.com) in 124 ms
O endereço de ns3.google.com foi obtido no servidor gtld retornado na seção adicional.
[~] dig @c.gtld-servers.net ns3.google.com
; <<>> DiG 9.7.3 <<>> @c.gtld-servers.net ns3.google.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62420
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 4, ADDITIONAL: 4
;; WARNING: recursion requested but not available
;; QUESTION SECTION:
;ns3.google.com. IN A
;; AUTHORITY SECTION:
google.com. 172800 IN NS ns2.google.com.
google.com. 172800 IN NS ns1.google.com.
google.com. 172800 IN NS ns3.google.com.
google.com. 172800 IN NS ns4.google.com.
;; ADDITIONAL SECTION:
ns2.google.com. 172800 IN A 216.239.34.10
ns1.google.com. 172800 IN A 216.239.32.10
ns3.google.com. 172800 IN A 216.239.36.10
ns4.google.com. 172800 IN A 216.239.38.10
;; Query time: 44 msec
;; SERVER: 192.26.92.30#53(192.26.92.30)
;; WHEN: Sat Sep 24 10:04:56 2011
;; MSG SIZE rcvd: 164