Я играю с NSLOOKUP, пытаясь узнать о рекурсивных поисках DNS. Я ищу фиктивное имя хоста и, кажется, получаю те же результаты, независимо от того, включаю я или отключаю рекурсию.
С рекурсией:
nslookup
Default Server: UnKnown
Address: ::1
> set recurse
> set debug
> nytimes
Server: UnKnown
Address: ::1
------------
Got answer:
HEADER:
opcode = QUERY, id = 2, rcode = NXDOMAIN
header flags: response, auth. answer, want recursion, recursion avail.
questions = 1, answers = 0, authority records = 1, additional = 0
QUESTIONS:
nytimes.intranet.contoso.com, type = A, class = IN
AUTHORITY RECORDS:
-> intranet.contoso.com
ttl = 3600 (1 hour)
primary name server = DNSSERVER.intranet.contoso.com
responsible mail addr = hostmaster.intranet.contoso.com
serial = 10301
refresh = 900 (15 mins)
retry = 600 (10 mins)
expire = 86400 (1 day)
default TTL = 3600 (1 hour)
------------
------------
Got answer:
HEADER:
opcode = QUERY, id = 3, rcode = NXDOMAIN
header flags: response, auth. answer, want recursion, recursion avail.
questions = 1, answers = 0, authority records = 1, additional = 0
QUESTIONS:
nytimes.intranet.contoso.com, type = AAAA, class = IN
AUTHORITY RECORDS:
-> intranet.contoso.com
ttl = 3600 (1 hour)
primary name server = DNSSERVER.intranet.contoso.com
responsible mail addr = hostmaster.intranet.contoso.com
serial = 10301
refresh = 900 (15 mins)
retry = 600 (10 mins)
expire = 86400 (1 day)
default TTL = 3600 (1 hour)
------------
------------
Got answer:
HEADER:
opcode = QUERY, id = 4, rcode = NOERROR
header flags: response, want recursion, recursion avail.
questions = 1, answers = 1, authority records = 0, additional = 0
QUESTIONS:
nytimes.contoso.com, type = A, class = IN
ANSWERS:
-> nytimes.contoso.com
internet address = 74.125.226.195
ttl = 1800 (30 mins)
------------
Non-authoritative answer:
------------
Got answer:
HEADER:
opcode = QUERY, id = 5, rcode = NOERROR
header flags: response, want recursion, recursion avail.
questions = 1, answers = 0, authority records = 1, additional = 0
QUESTIONS:
nytimes.contoso.com, type = AAAA, class = IN
AUTHORITY RECORDS:
-> contoso.com
ttl = 900 (15 mins)
primary name server = dns01.gpn.register.com
responsible mail addr = partnersupport.register.com
serial = 2002050701
refresh = 10800 (3 hours)
retry = 3600 (1 hour)
expire = 604800 (7 days)
default TTL = 3600 (1 hour)
------------
Name: nytimes.contoso.com
Address: 74.125.226.195
>
Без рекурсии:
nslookup
Default Server: UnKnown
Address: ::1
> set norecurse
> set debug
> nytimes
Server: UnKnown
Address: ::1
------------
Got answer:
HEADER:
opcode = QUERY, id = 2, rcode = NXDOMAIN
header flags: response, auth. answer, recursion avail.
questions = 1, answers = 0, authority records = 1, additional = 0
QUESTIONS:
nytimes.intranet.contoso.com, type = A, class = IN
AUTHORITY RECORDS:
-> intranet.contoso.com
ttl = 3600 (1 hour)
primary name server = DNSSERVER.intranet.contoso.com
responsible mail addr = hostmaster.intranet.contoso.com
serial = 10301
refresh = 900 (15 mins)
retry = 600 (10 mins)
expire = 86400 (1 day)
default TTL = 3600 (1 hour)
------------
------------
Got answer:
HEADER:
opcode = QUERY, id = 3, rcode = NXDOMAIN
header flags: response, auth. answer, recursion avail.
questions = 1, answers = 0, authority records = 1, additional = 0
QUESTIONS:
nytimes.intranet.contoso.com, type = AAAA, class = IN
AUTHORITY RECORDS:
-> intranet.contoso.com
ttl = 3600 (1 hour)
primary name server = DNSSERVER.intranet.contoso.com
responsible mail addr = hostmaster.intranet.contoso.com
serial = 10301
refresh = 900 (15 mins)
retry = 600 (10 mins)
expire = 86400 (1 day)
default TTL = 3600 (1 hour)
------------
------------
Got answer:
HEADER:
opcode = QUERY, id = 4, rcode = NOERROR
header flags: response, recursion avail.
questions = 1, answers = 1, authority records = 0, additional = 0
QUESTIONS:
nytimes.contoso.com, type = A, class = IN
ANSWERS:
-> nytimes.contoso.com
internet address = 74.125.226.195
ttl = 1526 (25 mins 26 secs)
------------
Non-authoritative answer:
------------
Got answer:
HEADER:
opcode = QUERY, id = 5, rcode = NOERROR
header flags: response, recursion avail.
questions = 1, answers = 0, authority records = 1, additional = 0
QUESTIONS:
nytimes.contoso.com, type = AAAA, class = IN
AUTHORITY RECORDS:
-> contoso.com
ttl = 626 (10 mins 26 secs)
primary name server = dns01.gpn.register.com
responsible mail addr = partnersupport.register.com
serial = 2002050701
refresh = 10800 (3 hours)
retry = 3600 (1 hour)
expire = 604800 (7 days)
default TTL = 3600 (1 hour)
------------
Name: nytimes.contoso.com
Address: 74.125.226.195
>
Похоже, он использует рекурсию, даже когда я отключил ее. Забавно то, что если я найду фиктивное имя хоста, указав 4.2.2.2 в качестве DNS-сервера, настройка рекурсии вступит в силу. Кто-нибудь знает, почему это происходит?
Кстати, я продезинфицировал имена хостов
Сервер возвращает авторитетные ответы для домена, когда у вас есть norecurse set, в дополнение к желанию выполнить за вас рекурсию. Не имеет значения, установлен ли флаг рекурсии или нет.
Получил ответ: HEADER: флаги заголовка: ответ, авт. ответ, рекурсивный доступ.