What is a DNS Record?

About

A DNS record is a row in a DNS database.

Example

Example of a A record.

api                                 IN A      164.132.99.202

where:

• api is a relative name
• IN is the INTERNET class (An other value is ANY)
• A is the A record
• 164.132.99.202 is the Ip address

If the apex domain is example.com, this entry will point the qualified domain name api.example.com to the ip 164.132.99.202

Syntax

A record is a text line.

<name> <ttl> <class> <type> <rdata>

• name is the name or IP address for a ptr record
• ttl is the the time to live in the cache
• class is the network class being used. No more used only for compatiblity
  • IN for Internet (The default and only)
  • HS for Hesiod (deprecated)
  • CH for Chaosnet (deprecated)
• type is the type of record
• rdata is output of the lookup

Type

¹⁾

Pointer

Pointer records that match a name to a destination:

• An A record maps a domain name to an IP address Version 4
• An AAAA'' record maps a domain name to an IP address Version 6.
• A CNAME record (Canonical Name) - map a name alias to a absolute/canonical name (alias system)
• NS - The DNS name server of the domain (where the DNS record of the domain are stored)

• ALIAS - Name to ip alias
• PTR - reverse - from IP to name

Extended

• CAA
• TXT
• NAPTR
• SRV Record (Service AutoDiscovery)
• LOC
• SSHFP
• TLAS

Mail

• What is a MX DNS record (Mail Exchanger Record)? - point to the mail server,
• SRV Record (Service AutoDiscovery) for email autodicovery

There is also a TXT record for each of the following mail authentication mechanism.

• What is the Sender Policy Framework (SPF) in Email?
• What is DKIM, the Email DomainKeys Identified Mail? (Mail Signatures)
• What is DMARC (Domain-based Message Authentication)?

Others

• ANY,
• SOA,

Query

A query is also known as a lookup. Check the lookup page to known how to perform a query.

Time To Live (TTL)

The Time To Live (TTL) of a DNS record is generally of 5 minutes.

If clients cache the results of host name lookups in order to achieve a performance improvement, they MUST observe the TTL information reported by DNS. Ref - DNS Spoofing ²⁾