DNS Records: A, CNAME, MX and Debugging Tips

When you type google.com into your browser, a complex chain of events occurs to translate that human-readable name into an IP address like 142.250.190.46. This system is DNS.

Common Record Types

A Record (Address)

Maps a domain name to an IPv4 address. This is the most fundamental record.
example.com → 93.184.216.34

CNAME (Canonical Name)

Maps one domain name to another domain name (an alias).
www.example.com → example.com

MX (Mail Exchange)

Specifies the mail servers responsible for accepting email on behalf of the domain.

TXT (Text)

Originally for human-readable notes, now heavily used for verification (Google Search Console, SPF records for email security).

Propagation and Caching

DNS records are cached at multiple layers (browser, OS, router, ISP) to improve speed. When you change a record, it can take up to 48 hours to "propagate" worldwide.

Additional Record Types

AAAA Record

The IPv6 equivalent of an A record. Maps a domain to an IPv6 address (128-bit, longer format).
example.com → 2001:0db8:85a3:0000:0000:8a2e:0370:7334

NS Record (Name Server)

Specifies which name servers are authoritative for the domain. These are the servers that hold the actual DNS records.

SOA Record (Start of Authority)

Contains administrative information about the domain, including the primary name server, administrator email, serial number, and refresh intervals.

PTR Record (Pointer)

Used for reverse DNS lookups - mapping IP addresses back to domain names. Essential for email server verification.

SRV Record (Service)

Specifies the location of services (like SIP, XMPP) running on a domain. Includes port numbers and priority.

DNS Resolution Process

When you visit a website, DNS resolution happens in several steps:

1. Browser Cache: Check if the domain was recently resolved
2. OS Cache: Check the operating system's DNS cache
3. Router Cache: Check your router's DNS cache
4. ISP DNS Server: Query your Internet Service Provider's DNS server
5. Root Name Servers: If not cached, query root servers for TLD information
6. TLD Name Servers: Query top-level domain servers (.com, .org, etc.)
7. Authoritative Name Servers: Query the domain's authoritative name servers
8. Return IP Address: The IP address is returned and cached at each level

This entire process typically takes milliseconds due to caching, but the first request can take longer.

DNS Security

DNSSEC (DNS Security Extensions)

Adds cryptographic signatures to DNS records to prevent spoofing and man-in-the-middle attacks. While not universally adopted, it's becoming more common for security-critical domains.

DNS over HTTPS (DoH) / DNS over TLS (DoT)

Encrypts DNS queries to prevent ISPs and attackers from seeing which websites you're visiting. This protects privacy but can complicate network monitoring and filtering.

Common DNS Issues

Propagation Delays

When you change DNS records, it can take time for changes to propagate worldwide. This is due to TTL (Time To Live) values that control how long records are cached. Typical propagation takes 4-48 hours, though most changes are visible within a few hours.

CNAME Conflicts

A CNAME record cannot coexist with other record types (A, MX, TXT) for the same name. This is a common mistake when setting up subdomains.

Email Delivery Issues

Incorrect MX records can cause email delivery failures. Common issues include:

• Missing MX records (fallback to A record, which may not be a mail server)
• Incorrect priority values (lower numbers = higher priority)
• Pointing to non-existent or misconfigured mail servers

Debugging DNS Issues

Is your site down, or is it just your local cache? Is your email not arriving because of a bad MX record? Here are common scenarios:

• Website not loading: Check A/AAAA records point to correct IP addresses
• Email not working: Verify MX records are correct and point to valid mail servers
• Subdomain issues: Ensure CNAME or A records are properly configured
• SSL certificate errors: Verify DNS records match certificate requirements

Use our DNS & WHOIS Lookup tool to query the authoritative nameservers directly, bypassing your local cache to see the true state of your domain records. This tool provides:

• All DNS record types (A, AAAA, CNAME, MX, TXT, NS, SOA)
• WHOIS information (domain registration details, expiration dates)
• Real-time queries (not cached results)
• Multiple record type queries in one request
• Detailed information for troubleshooting