DNS Record Types

A record and AAAA record

Indicates the IP address of a given domain.
A records hold IPv4 addresses.
AAAA record hold IPv6 addresses.

CNAME record

The ‘canonical name’ (CNAME) record.
Forwards one domain to another domain, it cannot be an IP address.
Only work for non-root domains, e.g. somethinghastogohere.mydomain.com.
- You can't have CNAME records without there being something where somethinghastogohereis.

Alias

Free of charge.
Native health checks.
You create alias records to route traffic to selected AWS resources, e.g. map your record name (example.com) to the DNS name for an AWS resource(elb1234.elb.amazonaws.com).
Works for root domains and non-root domains.
Alias record typically have a type of A or AAAA, but they work like a CNAME record.

NS record

Stands for ‘nameserver,’ and the nameserver record indicates which DNS server is authoritative for that domain.
NS records tell the Internet where to go to find out a domain's IP address.

TTL record

Time To Live (TTL) is kind of like an expiration date that is put on a DNS record.
Used to tell the recursive server or local resolver how long it should keep said record in its cache.
The longer the TTL = the longer the resolver holds that information in its cache; less traffic on DNS servers.
The shorter the TTL, the shorter amount of time the resolver holds that information in its cache; more traffic on DNS servers.
For example example.com has an A-record at the apex of the zone to point us to a server.
- With a TTL of 3600 seconds (1 hour), that means that as a recursive server learns about example.com, it will store that information about the A-record at example.com for one hour.
  - Anyone else who uses that same resolver will get the same answer, and on the authoritative side, there will be no query to the server unless the TTL runs out.
Lower TTL = Better for users with caching and when changing things related to DNS.

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Last updated 4 years ago

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Alias

Free of charge.

Native health checks.

You create alias records to route traffic to selected AWS resources, e.g. map your record name (example.com) to the DNS name for an AWS resource(elb1234.elb.amazonaws.com).

Works for root domains and non-root domains.

Alias record typically have a type of A or AAAA, but they work like a CNAME record.

TTL record

Time To Live (TTL) is kind of like an expiration date that is put on a DNS record.

Used to tell the recursive server or local resolver how long it should keep said record in its cache.

The longer the TTL = the longer the resolver holds that information in its cache; less traffic on DNS servers.

The shorter the TTL, the shorter amount of time the resolver holds that information in its cache; more traffic on DNS servers.

For example example.com has an A-record at the apex of the zone to point us to a server.

With a TTL of 3600 seconds (1 hour), that means that as a recursive server learns about example.com, it will store that information about the A-record at example.com for one hour.
- Anyone else who uses that same resolver will get the same answer, and on the authoritative side, there will be no query to the server unless the TTL runs out.

Lower TTL = Better for users with caching and when changing things related to DNS.