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Route53

Links: 101 AWS SAA Index

Introduction

  • It is a global service.

  • How DNS works

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  • Route 53 is fully managed, highly reliable, authoritative (the customer can update DNS records) DNS.

  • Route53 is also a domain registrar like GoDaddy.
This is the only service in AWS which provides 100% availability SLA.
It is called route 53 because it is reference to the traditional DNS port 53.
  • In Route53 we define records. Each records contains the following
    • Domain/subdomain name
    • Record types - A : IPv4 - AAAA: IPv6 - CNAME: maps one hostname to another. - NS: Name servers for the hosted zone. They control how traffic is routed to the domain.
    • IP Value
    • Route53 Routing Policies
    • TTL - amount of time record should be cached in DNS resolvers.
We can't create a CNAME record for the top node of a DNS namespace (Zone Apex)

Example: you can't create for example.com, but you can create for www.example.com

Hosted Zones

  • Hosted zones is a container for records which defines how to route traffic to a domain and its sub domains.
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  • We have two kinds of hosted zones public and private.
  • If we buy a public domain name then we use the public hosted zone.
  • Private hosted zones are for domain names that are not publicly available but are private. It can be only resolved by us in our VPC.
  • For any hosted zone we are going to pay 0.5$
  • Public and private hosted zones work in the exact same way, the only difference is that public hosted zones allow anyone from the internet to query your records where as in private hosted zone the records can be queried only from the VPC.

TTL

  • Stands for Time To Live

  • The client will cache the result for the duration of TTL. This means that in the duration of TTL the client will not make a DNS query for that particular domain.

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  • The idea behind TTL is that we don’t want to query the records too often since we don’t expect records to change a lot.

    • High TTL: 24 hours
      • less traffic on Route 53
      • outdated records.
    • Low TTL: 60 sec.
      • More traffic on Route 53 which means you will be paying more
      • Records are outdated for less time
      • Easy to change records

  • TTL will determine the amount you spend for Route 53 and how frequently the records should be updated.

TTL is mandatory for every record expect the alias records.

ALIAS

  • ALIAS points a hostname to an AWS resource.
    • It CANNOT be used for on premise resources.
  • You can use apex domain names with ALIAS.
  • It works for both root and non root domain. Eg: mydomain.com would work with ALIAS.
Route53 DOESNT charge for alias queries, they cost effective over CNAME.

They are free of charge

  • They have a native health check capability.
  • It is an extension of DNS functionality.
  • Alias records are always of type A or AAAA.
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  • You CANNOT set the TTL it is set automatically by Route53
For AWS resources always go for ALIAS over CNAME
  • ALIAS targets
    • Elastic Load Balancers
    • CloudFront Distributions
    • API Gateway
    • Elastic Beanstalk environments
    • S3 Websites
    • VPC Interface Endpoints
    • Global Accelerator accelerator
    • Route 53 record in the same hosted zone
You CANNOT set ALIAS record for EC2 DNS name
CNAME over ALIAS for 3rd party applications.

So, if you register the DNS name covid19survey.com, the zone apex is covid19survey.com. You can't create a CNAME record for covid19survey.com, but you can create an alias record for covid19survey.com that routes traffic to www.covid19survey.com.

An alias record can only redirect queries to selected AWS resources such as S3 buckets, CloudFront distributions, and another record in the same Route 53 hosted zone; however a CNAME record can redirect DNS queries to any DNS record. So, you can create a CNAME record that redirects queries from app.covid19survey.com to app.covid19survey.net.

A SysOps Administrator has been tasked with setting up a record set in Amazon Route 53 to point to an Application Load Balancer (ALB). The hosted zone and the ALB are in different accounts. What is the MOST cost-effective and efficient solution to this requirement?

Create an alias record in the hosted zone pointing to the Application Load Balancer.

  • It is possible to create an Alias record that points to a resource in another account.
  • CNAMEs records do incur costs and this is a less efficient solution as there is more complexity.

Last updated: 2023-03-14