Check DNS records on Windows with nslookup

  • Last updated on: 2016-06-27
  • Authored by: Rackspace Support

You might need to check the status of your DNS records for many reasons. For example, you might need to verify that any updates are correct or to troubleshoot issues accessing a particular service. Windows has a built-in tool for checking your DNS records, nslookup.

To access nslookup open up a command prompt window. Go to Start > All Programs > Accessories > Command Prompt.

Check for a record

To check for a specific record you need to specify the nslookup command, the record type — for example, A, MX, or TXT — and the host name you want to check. The following example shows how to check for any A records for rackspace.co.uk:

C:\Users\Administrator>nslookup -type=A rackspace.co.uk
Server:  cachens1.lon.rackspace.com>
Address:  83.138.151.80

Non-authoritative answer:

Name:    rackspace.co.uk
Address:  212.64.133.165

The first two lines of output specify the server to which the request was directed which is the default server that your system uses for DNS name resolution. The second section, which specifies a non-authoritative answer, gives the name of the record and the corresponding IP address. The answer is non-authoritative because the answer comes from a server, cachens1.lon.rackspace.com in this case, that is not the root source for those records.

Get an authoritative answer

To get an authoritative answer you need to go to the source. You can do this by specifying the authoritative name server at the end of the request.

Use the -type=soa option to tell nslookup to display the authoritative (primary) name server.

C:\Users\Administrator>nslookup -type=soa rackspace.co.uk
Server:  cachens1.lon.rackspace.com>
Address:  83.138.151.80

Non-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 -type=A rackspace.co.uk ns.rackspace.com
Server:  ns.rackspace.com
Address:  69.20.95.4

Name:    rackspace.co.uk
Address:  212.64.133.165

Check when a cached record will expire

DNS uses caching, which reduces the load on authoritative name servers but means that sometimes records can be out of date. If the authoritative and non-authoritative answers differ, you will have a cached response from the resolver name server you are using. The length of time that a record is cached depends on its time-to-live (TTL) value. This is a number 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 -type=A -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.com
Address:  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.uk
Address:  212.64.133.165
  • The first Got answer section of this example is used to get the hostname of the server from which you are requesting the A record from, in this case 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 for A 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 lists A records for the name servers listed in the authority records section

So from this response, you can see that the name server being used by the client computer will reuse the same A record for rackspace.co.uk for the next 4 minutes and 39 seconds. If you were to run the same command on the authoritative name server you would see what the current maximum TTL for the record is.

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