In most web hosting services, different types of DNS (Domain Name System) records are used to manage how domain names are translated into IP addresses and other information. In this writing, we will discuss about main types of DNS records : A, AAAA, CNAME.
TTL : Time to live. Tells how long the record should be cached by DNS resolvers or clients before being discarded or refreshed. It is measured in seconds. Why using TTL : caching (reduce DNS queries), propagation, performance.
1. A record :
■ Purpose : Maps a domain name to an IPv4 address.
■ Usage : Directing traffic to a website hosted on a server with an IPv4 address. Can use A record to add subdomain.
For example :
| Type | Name | Priority | Content | TTL |
|---|---|---|---|---|
| A | admin | 0 | 13.231.49.15 | 14400 |
If 13.231.49.15 refers to yamano-tech.jp, this A record creates subdomain admin.yamano-tech.jp
※ Please clarify that : subdomain # subpath
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2. AAAA record :
■ Purpose : Maps a domain name to an IPv6 address.
■ Usage : Necessary for websites hosted on servers using IPv6 addresses.
※ Mostly not used, IPv4 resource worldwide is still enough.*
3. CNAME record :
■ Purpose : Maps an alias name to a true canonical domain name (true domain name)
■ Usage : For example, any request to www.yamano-tech.jp will be resolved as if is were a request to yamano-tech.jp
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Use cases :
・Simplifying DNS Management
・Branding and SEO : Can have different domain names for branding purposes while managing them through a single canonical domain (true domain)
By pointing multiple aliases to a load balancer's canonical domain name, traffic can be efficiently distributed and managed.