DNS Records Explained: A, CNAME, MX, NS, TXT.

A Records

Address (A) records direct a hostname to a numerical IP address. For example, if you want mycomputer.yourdomain.com to point to your home computer (for instance, 192.168.0.3), you would enter a record that looks like this: Add A type record.

Note: If you have an IPv6 IP address, use an AAAA record instead.

Important: You must put a period after the hostname. Do not put periods after IP addresses.

CNAME Records

CNAME allows a machine to be known by one or more hostnames. There must always be an A record first, which is known as the canonical or official name. For example:

yourdomain.com. A 192.168.0.1

Using CNAME, you can point other hostnames to the canonical (A record) address. For example:

ftp.yourdomain.com. CNAME yourdomain.com.
mail.yourdomain.com. CNAME yourdomain.com.
ssh.yourdomain.com. CNAME yourdomain.com.

CNAME records make it possible to access your domain through ftp.yourdomain.com, mail.yourdomain.com, etc. Without a proper CNAME record, you will not be able to connect to your server using such addresses.

Entering a CNAME record

If we wanted home.help.com to point to help.com, we could enter the record this way:

Add CNAME type record and enter the subdomain. Do not put a period after the subdomain name.

Nameserver (NS) Records

NS records specify the authoritative nameservers for the domain.

Important: Changing NS records may cause your site to stop working. There is generally no need to change NS records via DirectAdmin.

Note: Any nameserver changes for domain names registered with Help.com.au can be managed via the Registrar section. This guide will help: https://support.help.com.au/managing-your-domain-and-web-hosting-on-help.com

MX Records

Free email services such as everyone.net require MX changes to be made for their software to work. This change allows mail destined for your domain to be directed to their server. Please note that changing MX records may prevent your current DirectAdmin hosted POP3 accounts, forwarders, autoresponders, and mailing lists from functioning.

Entering an MX record

To add an MX record, type in the hostname, as provided by the email provider. Then select the priority level (usually 10) from the dropdown box on the right. The priority level will also be provided by the email provider. Enter in the value or target in the text box next to where the value is added. Click “Add.”

To restore the original MX settings, enter yourdomain.com. and priority 0 after deleting the other MX record.

PTR Records

Pointer records (PTR) are used for reverse lookups. For example, to make 192.168.0.1 resolve to www.yourdomain.com, the record would look like this:

1.0.168.192.in-addr.arpa PTR www.yourdomain.com.

Note: The IP address is reversed in the first field. Please use a period after your hostname (second field).

The “in-addr.arpa” method is the most frequently used.

Important: PTR records are effective only if your site has its own IP address.

Important: PTR records are only effective if named.conf is manually edited and the proper zone information is added. This can only be done by a root user (the server admin).

TXT Records

Text records (TXT) are originally used for storing new types of information. This information could be any text. 

Note: TXT is often used to set up Sender Policy Framework (SPF) records, which are used to validate legitimate email sources from a domain. Example below: 

SRV Records

SRV records provide a standard way of allowing services to use different values and for a program to determine what those connection values are.

Example:

An SRV record contains the following information. Here, we list example values for each field.

An example SRV record:

_xmpp._tcp.example.com. 86400 IN SRV 10 5 5223 server.example.com.

In the above example, “_xmpp” indicates the type of service (the XMPP protocol) and “_tcp” indicates the TCP transport protocol, while “example.com” is the host, or the domain name. “Server.example.com” is the target server and “5223” indicates the port within that server.

SRV records must point to an A record (in IPv4) or an AAAA record (in IPv6). The server name they list cannot be a CNAME. So “server.example.com” must lead directly to an A or AAAA record under that name.

AAAA Records

AAAA records map a hostname to an IPv6 address, allowing identification of devices using IPv6.

DS Records

Delegation Signer (DS) records are used in DNSSEC to verify the authenticity of DNS records for a domain.

Example Format:

help.com. DS 12345 1 1 abcdef1234567890

Components:

1. Key Tag: Unique identifier for the DNSKEY.
2. Algorithm: Key generation algorithm (e.g., 1 for RSASHA1).
3. Digest Type: Type of digest (e.g., 1 for SHA-1).
4. Digest: Hash of the public key.

Important: Always include a period after the domain name. Ensure accuracy to maintain domain security.