Route 53 revision

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Some of the Route 53 (DNS) questions that I got caught out with...


What are all the different record types and what are they for?

Here's the list:



A kids AWS Route 53 record types alphabet rhyme...

A is for: an IPv4 address in dotted decimal notation.

AAAA is for:  an IPv6 address in colon-separated hexadecimal format. (4A's are better than 1A!)

CNAME is for:  (Wikipedia)  a domain name that is an alias for another domain, which is the "canonical" domain.

MX is for:  a mail server responsible for accepting email messages on behalf of a recipient's domain, and a preference value used to prioritize mail delivery if multiple mail servers are available. (from wikipedia)

NAPTR is for: who knows.

NS is for: the name servers for the hosted zone

PTR is for: Pointer records are used to map a network interface (IP) to a host name. These are primarily used for reverse DNS. (Wikipedia)

SOA is for: A start of authority (SOA) record provides information about a domain and the corresponding Amazon Route 53 hosted zone. Huh? Better description is:

An SOA record is a Start of Authority. Every domain must have a Start of Authority record at the cutover point where the domain is delegated from its parent domain. 

SPF is for: formerly used to verify the identity of the sender of email messages.
I.e. deprecated.  Instead of an SPF record, we recommend that you create a TXT record that contains the applicable value. For more information about valid values, see Sender Policy Framework, SPF Record Syntax.

SRV is for: A Service record (SRV record) is a specification of data in the Domain Name System defining the location, i.e. the hostname and port number, of servers for specified services.  (wiki)

TXT is for: A TXT record (short for text record) is a type of resource record in the Domain Name System (DNS) used to provide the ability to associate some arbitrary and unformatted text with a host or other name, such as human readable information about a server, network, data center, and other accounting information. (wiki)


What else did I get wrong? What's the main DNS protocol? Actually UDP, TCP is secondary for larger data sizes.

And what does Route 53 do (and not do?)

  • Register domain names – Your website needs a name, such as example.com. Amazon Route 53 lets you register a name for your website or web application, known as a domain name. For an overview, see How Domain Registration Works.
  • Route Internet traffic to the resources for your domain – When a user opens a web browser and enters your domain name in the address bar, Amazon Route 53 helps the Domain Name System (DNS) connect the browser with your website or web application. For an overview, see How Internet Traffic Is Routed to Your Website or Web Application.
  • Check the health of your resources – Amazon Route 53 sends automated requests over the Internet to a resource, such as a web server, to verify that it's reachable, available, and functional. You also can choose to receive notifications when a resource becomes unavailable and choose to route Internet traffic away from unhealthy resources. For an overview, see How Amazon Route 53 Checks the Health of Your Resources.
I.e. it doesn't do any sort of Load Balancing!


Weighted Routing Policy
Use the weighted routing policy when you have multiple resources that perform the same function (for example, web servers that serve the same website) and you want Amazon Route 53 to route traffic to those resources in proportions that you specify (for example, one quarter to one server and three quarters to the other). For more information about weighted resource record sets, see Weighted Routing.
Latency Routing Policy
Use the latency routing policy when you have resources in multiple Amazon EC2 data centers that perform the same function and you want Amazon Route 53 to respond to DNS queries with the resources that provide the best latency. For example, you might have web servers for example.com in the Amazon EC2 data centers in Ireland and in Tokyo. When a user browses to example.com, Amazon Route 53 chooses to respond to the DNS query based on which data center gives your user the lowest latency. For more information about latency resource record sets, see Latency-Based Routing.
Failover Routing Policy
Use the failover routing policy when you want to configure active-passive failover, in which one resource takes all traffic when it's available and the other resource takes all traffic when the first resource isn't available. For more information about failover resource record sets, see Configuring Active-Passive Failover by Using Amazon Route 53 Failover and Failover Alias Resource Record Sets. For information about creating failover resource record sets in a private hosted zone, see Configuring Failover in a Private Hosted Zone.



And a simpler summary of records including Alias records:

Q. Which DNS record types does Amazon Route 53 support? 
Amazon Route 53 currently supports the following DNS record types:
  • A (address record)
  • AAAA (IPv6 address record)
  • CNAME (canonical name record)
  • MX (mail exchange record)
  • NAPTR (name authority pointer record)
  • NS (name server record)
  • PTR (pointer record)
  • SOA (start of authority record)
  • SPF (sender policy framework)
  • SRV (service locator)
  • TXT (text record)
  • Additionally, Amazon Route 53 offers ‘Alias’ records (an Amazon Route 53-specific virtual record). Alias records are used to map resource record sets in your hosted zone to Amazon Elastic Load Balancing load balancers, Amazon CloudFront distributions, AWS Elastic Beanstalk environments, or Amazon S3 buckets that are configured as websites. Alias records work like a CNAME record in that you can map one DNS name (example.com) to another ‘target’ DNS name (elb1234.elb.amazonaws.com). They differ from a CNAME record in that they are not visible to resolvers. Resolvers only see the A record and the resulting IP address of the target record.




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