About the online NsLookup / Dig tool

The NsLookup / Dig tool provides a way of getting records for domains from the Domain Name System (DNS). It’s similar to the well-known NsLookup and Dig command line tools but is an independent, custom-crafted implementation for the Web.

Contents

• Form fields
  • domain
  • server
  • port
  • query type
  • query class
  • timeout
  • no recursion
  • advanced output
• Results
  • Query progress and response info
  • Header section
  • Questions section
  • Answer records
  • Authority records
  • Additional records

Form fields

domain

Specifies the domain name for which you want records. It can be any valid domain name, with or without a final dot, but the tool won’t run if the domain is blank. For the root domain, use a single dot (.).

If you enter an IP address, either IPv4 or IPv6, the tool will automatically convert it to the appropriate domain (typically used with query type PTR). For example, 10.1.0.52 would be converted to 52.0.1.10.in-addr.arpa.

server

Sets the server that should be queried for the DNS records. It can be a domain name, IPv4 address, or IPv6 address. The name default-resolver is a special name that the tool uses for its local resolver. If you’ve entered a different server, you can always go back to the default by entering default-resolver or just leaving the text box empty.

port

Sets the port number to use for the server. This defaults to 53, the standard port for DNS, and you’ll rarely have reason to change it.

query type

Indicates the type of resource records to retrieve for the domain. DNS queries normally get only one type of records for exactly one domain name. However, there are a couple of special query types to note:

ANY

This wildcard type asks the server for records of any type that it might have for the domain. Non-authoritative servers often just return whatever records they might have cached instead of forwarding the request to the authoritative server. Authoritative servers will usually return all the records for the domain name, though some major DNS providers have stopped honoring ANY requests and may return just a repurposed HINFO record to indicate the refusal.

AXFR

This special type requests a zone transfer, that is, a list of all records for the domain and its subdomains that the server might manage as a single zone. This query type can provide a lot of interesting information, but most servers will refuse this type.

query class

Indicates the class of resource records to retrieve for the domain. The non-Internet classes have little modern use, so you’ll rarely have a reason to change this option. The ANY class behaves much as the ANY type does, returning records of all classes for the domain. This isn’t as useful, however, because non-Internet types are rare.

timeout

Sets the timeout for the query in milliseconds and can’t exceed 30 000 ms (30 seconds). The default of 5000 ms (5 seconds) should be plenty for any normal query.

no recursion

Sets a flag in the query asking that the server not use recursion to get an answer.

Most DNS servers that act as resolvers will perform a sequence of queries behind the scenes to get the records you’re requesting. By setting the “no recursion” option, you’ll be asking the server to return whatever records it has (perhaps cached) and go looking no further.

advanced output

Causes the tool to show the Header section and Questions section for the response.

Results

Query progress and response info

The first few lines of the output simply indicate that the query is in progress or has finished. Once the query has completed, you’ll see a line showing the server that responded, whether or not the response was marked authoritative, and the time required to get the response.

Header section

This section, only shown when the advanced output option is selected, provides a breakdown of the DNS header information returned from the server.

Questions section

This section, only shown when the advanced output option is selected, shows the query details sent to the server and reflected in the server’s response.

Answer records

This section shows the answer records returned by the server. These records directly respond to the question; if you send a request for TXT records, for example, those TXT records will appear here (if they were available).

Authority records

This section shows records about authoritative servers for the queried domain name or the DNS zone it’s in.

Additional records

This section shows supplemental records that the server returned as a convenience or performance optimization. Typically these records provide IP addresses for domains mentioned in the Answer and Authority sections.

Be sure to check out our other free network tools at CentralOps.net and our Whois API at Hexillion.com.