Networking - DNS - Common Record Types

Common examples of DNS records include:

DNS Record	Function
A	A Records are the most basic type of DNS record. A Records are used to point a domain or subdomain to an IP address.
CNAME	CNAME records create an alias to an existing A record.
MX	Mail Exchanger (MX) records are used to help route email. MX records differ from A Records and CNAMEs in that they also require a “priority” value as a part of their entry.
NS	NS record are used to define which servers serve copies of a zone.
TXT	A TXT record is used to store text-based information (e.g., to hold SPF data and verify domain ownership).

A record

This record maps an IP Address to a hostname.

www      IN    A      192.168.1.12

CNAME record

Used to create an alias to an existing A record.

web     IN    CNAME  www

NOTE: You cannot create a CNAME record pointing to another CNAME record.

MX record

Used to define where email should be sent to.

@       IN    MX  1   mail.example.com.
mail    IN    A       192.168.1.13

NOTE: Must point to an A record, not a CNAME.

NS record

Used to define which servers serve copies of a zone.

@       IN    NS     ns.example.com.
@       IN    NS     ns2.example.com.
ns      IN    A      192.168.1.10
ns2     IN    A      192.168.1.11

NOTE: It must point to an A record, not a CNAME.

This is where Primary and Secondary servers are defined.

TXT record

Used to store text-based information:

example.com.   IN   TXT   "This domain name is reserved for use in documentation"
 
# The character string from a TXT record used for SPF:
"v=spf1 ip4:192.0.2.0/24 ip4:198.51.100.123 ip6:2620:0:860::/46 a -all"
 
# An example of use for DMARC:
"v=DMARC1;p=none;sp=quarantine;pct=100;rua=mailto:dmarcreports@example.com;"
 
# Use for site verification:
"google-site-verification=6P08Ow5E-8Q0m6vQ7FMAqAYIDprkVV8fUf_7hZ4Qvc8"
 
# Use for custom email service:
_amazonses.example.com.   IN   TXT   "pmBGN/7MjnfhTKUZ06Enqq1PeGUaOkw8lGhcfwefcHU="

NOTE: Text records can be used:

for sources outside of your domain.
to hold SPF data and verify domain ownership.

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