Route 53

  • Route 53 FAQ
  • Route 53 is named after the fact that DNS is on port 53
  • There is a limit of 50 domain names on Route 53 – this can be extended by contacting AWS support


  • CNAME (Canonical Name) can be used to map aliases to true (canonical) domain name
  • A Record (Address Record) for resolving a domain name to an IP address
  • Alias records are an AWS / Route 53 specific term, similar to CNAME with the key distinction that CNAMEs can’t be used on the zone apex (root domain i.e. cnames could be used against, but not against – for this you’d need to use either an A Record or Alias record)

Tip for the exam: if you’re given the option to choose between CNAME and Alias record, choose the Alias record.

ELBs and Route 53

  • ELBs operate on domain names only, and never have fixed IPv4 or IPv6 addresses. This means that it’s not possible to use an A Record to resolve to an ELB. You must use an Alias record; Alias records were created for this purpose.

Routing Policies

A- Simple Routing

    • Only one record with multiple IP addresses
    • If you specify multiple values in a record, Route53 returns all values to the user in a random order.

B- Weighted Routing

    • Map one domain to one or more domains
    • e.g direct 20% of traffic to an ELB in us-east-1, and 80% of traffic to an ELB in us-west-1
    • Good for A/B testing where you want to test a different website for a certain proportion of your users
    • The weights are relative to each other, so they can be arbitrary values, not necessarily adding up to 100

C – Latency Based Routing

    • Allows you to route traffic based on the lowest network latency for your end user (i.e which region will give them the fastest response time).
    • To use latency-based routing, you create a latency resource record set for the Amazon EC2 (ELB) resource in each region that hosts your website. When Amazon Route 53 receives a query for your site, it selects the latency resource record set for the region that gives the user the lowest latency. Route 53 then responds with the value associated with that resource record set.
    • Map one domain to one or more domains
    • Route traffic based on latency. i.e. if your ping to eu-west-2 is 300ms and the ping to ap-southeast-2 is 54ms, Latency Based Routing rules can be set to direct traffic to the lower latency region, ap-southeast-2

D- Failover Routing Policy

    • If you have multiple resources that perform the same function, you can configure DNS failover so that Route 53 will route your traffic from an unhealthy resource to a healthy resource. For example, if your EC2 instance becomes unhealthy, you could:
      • Failover to a healthy EC2 instance, or…
      • Failover to a static website hosted in an S3 bucket.
    • Make sure you have a health check defined for the failover
    • For DR (disaster recovery)
    • When you want to configure active-passive failover
    • Primary is “active”, secondary is “passive”/DR

E- Geolocation Routing Policy

  • Lets you choose where your traffic will be sent based on the geographic location of your users (i.e. the location from which DNS queries originate) For example, you might want all queries from Europe to be routed to a fleet of EC2 instances that are specifically configured for European customers. These servers may have the local language of your European customers and all prices are displayed in Euros.

F- Geoproximity Routing (Traffic Flow Only)

  • Lets Amazon Route 53 route traffic to your resources based on the geographic location of your users and your resources. You can also optionally choose to route more traffic or less to a given resource by specifying a value, known as a bias. A bias expands or shrinks the size of the geographic region from which traffic is routed to a resource.
  • You must use Route 53 traffic flow to use this routing type

G- Multivalue Answer Policy

    • Lets you configure Amazon Route 53 to return multiple values, such as IP addresses for your web servers, in response to DNS queries. You can specify multiple values for almost any record, but multivalue answer routing also lets you check the health of each resource, so Route 53 returns only values for health resources. 
    • Similar to simple routing however it allows you to put health checks on each record set.
    • For returning multiple values such as IP addresses for healthy resources

Health Checks

    • We can set health checks on individual record sets
    • If a record set fails a health check it will be removed from Route 53 until it passes the health check
    • You can set SNS notifications to alert you if a health check is failed.

Q & A

Question 1: Which of the following Route 53 policies allow you to a) route data to a second resource if the first is unhealthy, and b) route data to resources that have better performance?

A. Failover routing and simple routing
B. Geoproximity Routing and Geolocation routing
C. Geolocation routing and latency-based routing
D. Failover routing and latency-based routing

Question 2: Route53 is Amazon’s DNS Service.

A. True
B. False

Question 3: Route53 is named so because ________.

A. It was invented in 1953
B. Route 66 was already registered with microsoft
C. The DNS port is on port 53 and Route53 is a DNC service
D. Beats me: only people marketing can tell you the reason behind its name

Question 4: You have created a new subdomain for your popular website, and you need this subdomain to point to an Elastic Load Balancer using Route53. Which DNS record set should you create?

A. A

Question 5: True or False: There is a limit to the number of domain names that you can manage using Route 53.

A. True – there is a hard limit of 10 domain names. You can’t go above this number
B. True and False. With Route53, there is a default limit of 50 domain names . However. This limit can be increased by contacting AWS support.
C. False. By default, you can support as many domain names on Route 53 as you want

Question 6: You are hosting a website and would like visitors from the United Kingdom to see a different site than those in Australia. Which Routing Policy would help you to accomplish this?

A. Faliover routing policy
B. Geolocation routing policy
C. Geoproximity routing policy
D. Latency routing policy

Question 7: Your company hosts 10 web servers all serving the same web content in AWS. They want Route 53 to serve traffic to random web servers. Which routing policy will meet this requirement, and provide the best resiliency?

A. Simple routing
B. Weighted routing
C. Multivalue routing
D. Latency routing

Route 53 Answers

1- D 2-A 3-C 4-D 5-C 6-B 7-C