DNS Records - A Quick Guide

DNS stands for Domain Name System. This is a service that translates domain names and domain zones into IP addresses. This is due to the way that computers work. A domain name such as domain.com is easier to remember than an IP address (e.g. 194.34.34.146). A Domain name is just an alias which fundamentally points to a computer (via an IP Address). Each domain name has a complex array of DNS settings which can set where a website points to, where a sub-domain points to, where your email points to and more. DNS records are stored in a zone file; this is where your record information is stored for your domain to point to the correct server or mail server.

DNS Record Types

Your domain name registrar will allow you to manage a whole variety of DNS Zone records. By setting a zone record it provides information about a specific object. A list of most common records are provided below:

• Address Mapping records (A)

  The record A specifies IP address (IPv4) for given host. A-records are used for conversion of domain names to corresponding IP addresses.

• IP Version 6 Address records (AAAA)

  The record AAAA (also quad-A record) specifies IPv6 address for given host. So it works the same way as the A record and the difference is the type of IP address.

• Canonical Name records (CNAME)

  The CNAME record specifies a domain name that has to be queried in order to resolve the original DNS query. Therefore CNAME records are used for creating aliases of domain names. CNAME records are truly useful when we want to alias our domain to an external domain. In other cases, we can remove CNAME records and replace them with A records and even decrease performance overhead.

• Host Information records (HINFO)

  HINFO records are used to acquire general information about a host. The record specifies type of CPU and OS. The HINFO record data provides the possibility to use operating system specific protocols when two hosts want to communicate. For security reasons the HINFO records are not typically used on public servers.

  Note: Standard values in RFC 1010

• Integrated Services Digital Network records (ISDN)

  The ISDN resource record specifies ISDN address for a host. An ISDN address is a telephone number that consists of a country code, a national destination code, a ISDN Subscriber number and, optionally, a ISDN subaddress. The function of the record is only variation of the A resource record function.

• Mail exchanger record (MX)

  The MX resource record specifies a mail exchange server for a DNS domain name. The information is used by Simple Mail Transfer Protocol (SMTP) to route emails to proper hosts. Typically, there are more than one mail exchange server for a DNS domain and each of them have set priority.

  Example:

  msn.com MX preference = 5, mail exchanger = mx2.hotmail.com
  msn.com MX preference = 5, mail exchanger = mx3.hotmail.com
  msn.com MX preference = 5, mail exchanger = mx4.hotmail.com
  msn.com MX preference = 5, mail exchanger = mx1.hotmail.com
  msn.com nameserver = ns3.msft.net
  msn.com nameserver = ns5.msft.net
  msn.com nameserver = ns4.msft.net
  msn.com nameserver = ns1.msft.net
  msn.com nameserver = ns2.msft.net
  mx1.hotmail.com internet address = 65.55.92.184
  mx1.hotmail.com internet address = 65.54.188.72
  mx1.hotmail.com internet address = 65.54.188.94
  mx1.hotmail.com internet address = 65.54.188.110
  mx1.hotmail.com internet address = 65.54.188.126
  mx1.hotmail.com internet address = 65.55.37.72
  mx1.hotmail.com internet address = 65.55.37.88
  mx1.hotmail.com internet address = 65.55.37.104
  mx1.hotmail.com internet address = 65.55.37.120
  mx1.hotmail.com internet address = 65.55.92.136
  mx1.hotmail.com internet address = 65.55.92.152
  mx1.hotmail.com internet address = 65.55.92.168

• Name Server records (NS)

  The NS record specifies an authoritative name server for the given host. If you set a name-server which is not your Domain Registrar - it is possible to define a whole new Zone file on another server. These settings will overwrite the NS settings outlined though your domain control panel. These NS can be set via a Hosting control panel such as cPanel.

• Reverse-lookup Pointer records (PTR)

  As opposed to forward DNS resolution (A and AAAA DNS records), the PTR record is used to look up domain names based on an IP address.

• Start of Authority records (SOA)

  The record specifies core information about a DNS zone, including the primary name server, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone.

• Text records (TXT)

  The text record can hold arbitrary non-formatted text string. Typically, the record is used by Sender Policy Framework (SPF) to prevent spoof emails being sent from your own email account.