A and cname records in dns

A record and CNAME are one of the most common types of records when you want to deploy your domain or subdomain on the internet.

Use-cases and restrictions

A record

A record is an abbreviation for "Address". The address you type when you go to a website, send an email or connect to Twitter, Facebook or Instagram. There are many things you can do with A records, including using multiple A records for the same domain to offer redundancy and fallbacks. Furthermore, many names may point to the same IP address, in which case each will have its own A record pointing to the same IP address.

Use-cases

• Use an A record if you manage which IP addresses are assigned to a particular machine, or if the IP are fixed (this is the most common case).

CNAME record

A CNAME is a database entry in the Domain Name System (DNS) that indicates that one domain name is a alias for another. The CNAME, often known as the "true name" is especially crucial when multiple services are running from the same IP address.

Use-cases

• To direct people to the main website from many websites owned by the same individual or organization.
• To assign a unique hostname to each network service, such as File Transfer Protocol (FTP) or email, and point it to the root domain.
• To assign a subdomain to each customer on the domain of a single service provider and use CNAME to point the subdomain to the customer's root domain.
• To register the same domain in many countries and direct each country's version to the main domain.

Restrictions

• A CNAME record should always link to another domain name rather than an IP address.
• A CNAME record cannot exist alongside another record with the same name. It is not feasible for www.example.com to have both a 'CNAME' and a 'TXT' record.
• A CNAME can point to another CNAME. However, this is not normally advised for performance reasons. To prevent needless performance overheads, the CNAME should point as nearly as feasible to the destination name when relevant.

References

• https://support.dnsimple.com/articles/differences-between-a-cname-alias-url/
• https://support.dnsimple.com/categories/dns/
• https://www.elegantthemes.com/blog/wordpress/what-is-an-a-record-and-how-is-it-different-from-cname-and-mx
• https://www.cloudflare.com/learning/dns/dns-records/#:~:text=What%20is%20a%20DNS%20record,handle%20requests%20for%20that%20domain.