DNS Records

DNS Records

Learning Objectives

After reading this article you will be able to:

  • Identify several types of DNS records

What is a DNS record?

DNS records (aka zone files) are instructions that live in authoritative DNS servers and provide information about a domain including what IP address is associated with that domain and how to handle requests for that domain. These records consist of a series of text files written in what is known as DNS syntax. DNS syntax is just a string of characters used as commands which tell the DNS server what to do. All DNS records also have a ‘TTL’, which stands for time-to-live, and indicates how often a DNS server will refresh that record.

You can think of a set of DNS records like a business listing on Yelp, that listing will give you a bunch of useful info about a business such as their location, hours, services offered, etc. All domains are required to have at least a few essential DNS records for a user to be able to access their website using a domain name, and there are several optional records that serve additional purposes.

What are the most common types of DNS record?

What are some of the less commonly used DNS records?

  • AFSDB record - This record is used for clients of the Andrew File System (AFS) developed by Carnegie Melon. The AFSDB record functions to find other AFS cells.
  • APL record - The ‘address prefix list’ is an experiment record that specifies lists of address ranges.
  • CAA record - This is the ‘certification authority authorization’ record, it allows domain owners state which certificate authorities can issue certificates for that domain. If no CAA record exists, then anyone can issue a certificate for the domain. These records are also inherited by subdomains.
  • DNSKEY record - The ‘DNS Key Record’ contains a public key used to verify Domain Name System Security Extension (DNSSEC) signatures.
  • CDNSKEY record - This is a child copy of the DNSKEY record, meant to be transferred to a parent.
  • CERT record - The ‘certificate record’ stores public key certificates.
  • DCHID record - The ‘DHCP Identifier’ stores info for the Dynamic Host Configuration Protocol (DHCP), a standardized network protocol used on IP networks.
  • DNAME record - The ‘delegation name’ record creates a domain alias, just like CNAME, but this alias will redirect all subdomains as well. For instance if the owner of ‘example.com’ bought the domain ‘website.net’ and gave it a DNAME record that points to ‘example.com’, then that pointer would also extend to ‘blog.website.net’ and any other subdomains.
  • HIP record - This record uses ‘Host identity protocol’, a way to separate the roles of an IP address; this record is used most often in mobile computing.
  • IPSECKEY record - The ‘IPSEC key’ record works with the Internet Protocol Security (IPSEC), an end-to-end security protocol framework and part of the Internet Protocol Suite (TCP/IP).
  • LOC record - The ‘location’ record contains geographical information for a domain in the form of longitude and latitude coordinates.
  • NAPTR record - The ‘name authority pointer’ record can be combined with an SRV record to dynamically create URI’s to point to based on a regular expression.
  • NSEC record - The ‘next secure record’ is part of DNSSEC, and it’s used to prove that a requested DNS resource record does not exist.
  • RRSIG record - The ‘resource record signature’ is a record to store digital signatures used to authenticate records in accordance with DNSSEC.
  • RP record - This is the ‘responsible person’ record and it stores the email address of the person responsible for the domain.
  • SSHFP record - This record stores the ‘SSH public key fingerprints’; SSH stands for Secure Shell and it’s a cryptographic networking protocol for secure communication over an unsecure network.

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