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There are many reasons why you might need to check the status of your Domain
Name System (DNS) records. For example, you might need to verify that updates
are correct or troubleshoot issues with accessing a service.
If you're a Cloud DNS user, you can
view your DNS records through the Cloud ControlPanel. In addition, Microsoft® Windows®
offers nslookup
, a built-in tool for checking your DNS records from the
command line.
To access nslookup
, open a command prompt window by selecting Start >
All Programs > Accessories > Command Prompt.
Check a DNS record
Check a DNS record
To check a specific DNS record, you need to specify the nslookup
command,
an optional record type (for example, A
, MX
, or TXT
), and the host name
that you want to check.
Note: If you omit the record type, it defaults to A
.
The following example shows how to check A
records for rackspace.co.uk:
C:\Users\Administrator>nslookup rackspace.co.ukServer: cachens1.lon.rackspace.com>Address: 83.138.151.80Non-authoritative answer:Name: rackspace.co.ukAddress: 212.64.133.165
The first two lines of output specify the server to which the request
was directed. This server is the default server that your system uses for DNS
name resolution.
The second section gives the name of the record and the corresponding Internet
Protocol (IP) address. However, the answer in this section is
non-authoritative because it originates from a server
(cachens1.lon.rackspace.com) that isn't the root source for those records.
Get an authoritative answer
Get an authoritative answer
To get an authoritative answer you need to specify the authoritative (primary)
name server at the end of the request.
Use the -type=soa
option to tell nslookup
to display the
authoritative name server, as shown in the following example:
C:\Users\Administrator>nslookup -type=soa rackspace.co.ukServer: cachens1.lon.rackspace.com>Address: 83.138.151.80Non-authoritative answer:rackspace.co.uk primary name server = ns.rackspace.com responsible mail addr = hostmaster.rackspace.com serial = 1415913000 refresh = 3600 (1 hour) retry = 300 (5 mins) expire = 1814400 (21 days) default TTL = 300 (5 mins)ns.rackspace.com internet address = 69.20.95.4
The address labeled primary name server
is the DNS authority for the
domain.
If you add the address of the authoritative name server
(ns.rackspace.com) to the first command, the record is now checked
against that name server.
C:\Users\Administrator>nslookup rackspace.co.uk ns.rackspace.comServer: ns.rackspace.comAddress: 69.20.95.4Name: rackspace.co.ukAddress: 212.64.133.165
Check when a cached record expires
Check when a cached record expires
DNS uses caching, which reduces the load on authoritative name servers.
However, as a result, records might be outdated. If the authoritative and
non-authoritative answers differ, you have a cached response from the resolver
name server that you're using. The length of time that a record is cached
depends on its time-to-live (TTL) value. The TTL is a number that is
specified in seconds.
To see how long a record is cached, include the debug
option, as shown in
the following example:
C:\Users\Administrator>nslookup -debug rackspace.co.uk------------Got answer:HEADER: opcode = QUERY, id = 1, rcode = NOERROR header flags: response, want recursion, recursion avail. questions = 1, answers = 1, authority records = 2, additional = 2 QUESTIONS: 80.151.138.83.in-addr.arpa, type = PTR, class = IN ANSWERS: -> 80.151.138.83.in-addr.arpa name = cachens1.lon.rackspace.com ttl = 2466 (41 mins 6 secs) AUTHORITY RECORDS: -> 151.138.83.in-addr.arpa nameserver = ns2.rackspace.com ttl = 2466 (41 mins 6 secs) -> 151.138.83.in-addr.arpa nameserver = ns.rackspace.com ttl = 2466 (41 mins 6 secs) ADDITIONAL RECORDS: -> ns.rackspace.com internet address = 69.20.95.4 ttl = 12982 (3 hours 36 mins 22 secs) -> ns2.rackspace.com internet address = 65.61.188.4 ttl = 12985 (3 hours 36 mins 25 secs)------------Server: cachens1.lon.rackspace.comAddress: 83.138.151.80------------Got answer: HEADER: opcode = QUERY, id = 2, rcode = NOERROR header flags: response, want recursion, recursion avail. questions = 1, answers = 1, authority records = 2, additional = 2 QUESTIONS: rackspace.co.uk, type = A, class = IN ANSWERS: -> rackspace.co.uk internet address = 212.64.133.165 ttl = 279 (4 mins 39 secs) AUTHORITY RECORDS: -> rackspace.co.uk nameserver = ns.rackspace.com ttl = 17465 (4 hours 51 mins 5 secs) -> rackspace.co.uk nameserver = ns2.rackspace.com ttl = 17465 (4 hours 51 mins 5 secs) ADDITIONAL RECORDS: -> ns.rackspace.com internet address = 69.20.95.4 ttl = 15754 (4 hours 22 mins 34 secs) -> ns2.rackspace.com internet address = 65.61.188.4 ttl = 15727 (4 hours 22 mins 7 secs)------------Non-authoritative answer:Name: rackspace.co.ukAddress: 212.64.133.165
The response includes the following information:
- The first
Got answer
section of this example is used to get the
host name of the server from which you are requesting theA
record.
In this example, the host name is cachens1.lon.rackspace.com. - The second
Got answer
section relates to your actual request. - The
HEADER
section contains details about the type of request and
its success. - The
QUESTIONS
section shows that the request was forA
records
for rackspace.co.uk. - The
ANSWERS
section displays one record with an IP address of
212.64.133.165 and a TTL of 279 seconds (4 minutes 39 seconds). - The
AUTHORITY RECORDS
section specifies the name servers that
correspond to the domain. - The
ADDITIONAL RECORDS
section listsA
records for the name servers
that are listed in the authority records section.
This response shows that the name server that the client computer uses will
reuse the same A
record for rackspace.co.uk for the next 4 minutes and 39
seconds. If you run the same command on the authoritative name server, you
see the current maximum TTL for the record.
Updated 5 months ago