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Useful tools for DNS troubleshooting

Domain Name System – a hierarchical distributed network name system that responds to domain name queries. Thanks to DNS, the domain name is translated into the corresponding IP address.

How the DNS server works

  • The user enters the website address in the browser.
  • Browser sends a query to the DNS server asking you to return the IP address for the selected domain
  • The DNS server in response returns the IP address of the server to which the indicated domain is assigned.
  • The browser establishes a connection to the server with a specific IP address asking for a page to display for the domain

What DNS records are used for

In addition to the main task, which is the translation of names to the IP address using DNS records, you can create and redirect subdomains, e.g. the email service can be redirected to another server.

What is the DNS record made of

  • Name – domain, domain
  • Type – determines the type of record that will be or is already defined.
  • TTL (Time to Live) – this is the time to store the record in DNS servers expressed in seconds.
  • Priority – determines the order and value of the entry. It is used at the MX record.
  • Value – this is a parameter that determines the value of a specific record. Depending on the type of record, this information will vary, for example. IP, host or text information.

The most important types of DNS records

  • A (Address) record is one of the main records pointing to the IPv4 (32-bit) server on the network.
  • AAAA record – is a record pointing to the IP address of the server, but in the IPv6 version (128-bit).
  • CNAME (Canonical Name) – this is a replacement entry for record A, where the host address is given instead of the IP address.
  • MX record (mail eXchange) – is the address of the mail server. With this record, you can redirect email traffic in a given domain to another server.
  • NS (Name Server) record – DNS server address.
  • SOA (Start Of Authority) is a record containing the main address of the Domain Name System server.
  • TXT (Text) record – an entry that allows you to add any text to a domain record. Often used to verify ownership of a domain in Google apps.

nslookup command

We use nslookup to obtain DNS records of a domain name, such as mapping between a domain name and a related IP address
nslokup domain_name
The first section displays the information about the server used to obtain DNS records. The second one displays us a fully qualified domain name and corresponding IP address (both IPv4 and IPv6)

dig command

Abbreviated from Domain Information Groper, Dig is another command-line tool for sending queries to domain nameserver (DNS) servers. dig allows you to search for DNS and provide detailed information about different DNS records, including A, MX, and SOA records.
dig domain_name

MXToolBox

MXToolBox is a free online tool (payable for additional features) that provides fast and accurate network diagnostics and DNS search tools.

IntoDNS

IntoDNS is another valuable tool that you can use to check and troubleshoot any DNS issues.
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