What do DNS records mean?

DNS records (Resource Records, RR) are fundamental blocks of the Domain Name System (DNS), containing information about domains, their correspondence to IP addresses, resource locations, etc.

Main record types:

• A: Maps a hostname (e.g., www.example.com) to an IPv4 address.
• AAAA: Maps a hostname to an IPv6 address.
• CNAME: Creates an alias for another domain name. Used for redirecting subdomains or simplifying management of multiple services.
• MX: Specifies mail servers responsible for receiving email for the domain. Contains priority for each server.
• PTR: Reverse DNS record, maps an IP address to a hostname. Used in reverse zones of DNS.
• TXT: Stores textual information used for various purposes, such as domain verification, SPF (Sender Policy Framework), or DKIM (DomainKeys Identified Mail) for email protection.
• NS: Indicates authoritative name servers for the domain. Each domain must have at least two NS records.
• SOA: "Start of Authority" record contains administrative information about the domain, such as the contact address of the administrator, zone serial number, refresh time, etc.

Example record structure:

name    TTL   class  type  rdata

• name: Resource name (e.g., www).
• TTL (Time To Live): Time in seconds during which records can be cached by resolvers.
• class: Protocol family. Most often IN (Internet).
• type: Record type (A, AAAA, CNAME, etc.).
• rdata: Data specific to the record type (e.g., IP address for A record).

Example DNS zone configuration file (bind-compatible format):

$ORIGIN example.com.
$TTL 3600
@       IN      SOA     ns1.example.com. admin.example.com. (
                        2023102701      ; Serial
                        3600            ; Refresh
                        1800            ; Retry
                        604800          ; Expire
                        86400 )         ; Minimum TTL
        IN      NS      ns1.example.com.
        IN      NS      ns2.example.com.

@       IN      A       192.168.1.1
www     IN      A       192.168.1.2
mail    IN      A       192.168.1.3
        IN      MX      10 mail.example.com.