DNS records explained: A, AAAA, CNAME, SRV, TXT, MX and PTR

DNS turns names like example.cz into the IP addresses computers understand. This article explains what each record type does, why a change doesn't take effect right away and how to check a record yourself. The guides on a domain for your VPS and a domain for your Minecraft server build on these basics.

How DNS works#

When a player types mc.example.cz into Minecraft, or a visitor types example.cz into a browser, their computer asks a resolver (their internet provider's DNS server, or a public one such as 1.1.1.1). The resolver looks up which authoritative DNS server holds the domain's records, asks it, and stores the answer for a while.

Three roles that often get mixed up:

Record types#

A and AAAA#

The foundation of everything: they say which IP address a name points to. You'll find your VPS's IPv4 address in the customer area in the Network tab (for example 203.0.113.10), and the IPv6 address there too (for example 2001:db8::10).

Add an AAAA record only if the service behind the name really listens on the IPv6 address. Devices with IPv6 usually try IPv6 first.

CNAME#

A CNAME says “this name is just another name for that name”. Typically www.example.cz as an alias for example.cz. The resolver then looks up the A/AAAA record of the target name.

Rules:

• A name with a CNAME can't have any other record (per the DNS standard, RFC 1034). That's why a CNAME can't be placed at the domain root (example.cz), where there are always NS and SOA records.
• Some DNS providers work around this with their own feature (Cloudflare calls it CNAME flattening): at the root they return the target's IP address directly.

SRV#

An SRV record says which name and port a specific service runs on. Minecraft Java Edition uses it, for example: thanks to it, players don't have to type the port.

_minecraft._tcp.mc.example.cz.  300  IN  SRV  0 5 25570 mc.example.cz.

In a DNS provider's web interface the fields have similar names (Name / Service / Protocol, Priority, Weight, Port, Target). The full procedure for Minecraft is in Server address and custom domain. Bedrock Edition doesn't use SRV records.

MX and TXT#

• MX sets the domain's mail server. The lower number (priority) wins. The target must be a name with an A/AAAA record.
• TXT carries text. Services such as Google or Microsoft use it to verify that you own the domain. Email uses it for SPF (who may send mail for the domain), DKIM (message signing) and DMARC (what to do with forged messages, the _dmarc.example.cz record).

Domain root and subdomains#

• The root (also the “apex”, @) is the domain itself, example.cz.
• A subdomain is anything in front of it: www.example.cz, mc.example.cz, panel.example.cz. You don't have to “create” a subdomain anywhere; just add a record for it.
• An asterisk (*.example.cz) is a wildcard record for all names that don't have their own record.

A trailing dot (example.cz.) in zone file notation means “the full name, don't add anything”. In web interfaces you usually don't need to type it; if the interface requires the dot, it will tell you.

TTL and “propagation”#

TTL (time to live) is the number of seconds resolvers may remember an answer. When you change a record, a resolver that currently remembers it keeps returning the old value until its TTL expires. This is what's commonly called “DNS propagation”.

Two more situations:

• Changing nameservers at the registrar takes longer, usually up to 24 hours.
• Negative answers are remembered too. If someone asks for a name before the record exists, the resolver remembers “no such name” for a while. So create the record first and only then test it.

How to check a record#

Replace example.cz and mc.example.cz in the commands with your own domain.

Useful public resolvers for checking: 1.1.1.1 (Cloudflare), 8.8.8.8 (Google), 9.9.9.9 (Quad9). If the new record shows up there but not for you, you have an old answer in your cache.

Common mistakes#

Troubleshooting#

Non-existent domain (Windows) or NXDOMAIN (dig)#

The name doesn't exist. Check for typos, that the record is saved and that you're editing it with the right nameservers. If you asked for the name before you created the record, wait a few minutes (a negative answer in the cache).

The answer is empty, but the name exists (No answer, ANSWER: 0)#

The name exists, but it has no record of the type you're asking for. For example, you have an A record but are asking for AAAA. Each tool shows it a little differently:

• dig +short prints nothing. The full dig output shows status: NOERROR and ANSWER: 0.
• nslookup on macOS and Linux prints *** Can't find …: No answer.
• nslookup on Windows prints only details about the domain's nameserver instead of an address (the primary name server line).

For SRV, check that the name contains _minecraft._tcp. and the right subdomain.

1.1.1.1 shows the new IP, but I still get the old one#

Your computer or internet provider has an old answer in its cache. Wait for the TTL to expire, or clear your computer's cache:

Browsers have their own cache; closing and reopening them helps.

dig: command not found or nslookup: command not found#

On Linux, install the bind9-dnsutils package (see the Linux tab above). On Windows, use nslookup or Resolve-DnsName instead of dig.

The change hasn't taken effect even after several hours#

1. Find the domain's nameservers: dig +short example.cz NS (Windows: nslookup -type=NS example.cz).
2. Check that you're editing the records with the same provider the NS points to.
3. Ask the nameserver directly (see “Advanced” above). If the record isn't there, the change wasn't saved.

Further reading#

• Cloudflare: DNS record types (opens in a new window)
• Microsoft: the nslookup command (opens in a new window)
• Ubuntu: dig manual page (opens in a new window)