Route 53

Question 1

Describe Route 53

Answer 1

Route 53 is a high available, scalable, full managed and Authoritative DNS

Authoritative DNS means that you (the customer) can update the DNS records

It is also a Domain Registrar

Question 2

Name 4 record types and what they do

Answer 2

A - maps a hostname to IPv4

AAAA - MAPS HOSTNAME TO ipV6

CNAME - maps hostname to another hostname

NS - name servers for the hosted zone

Question 3

TTL stands for?

Answer 3

Time to Live

Question 4

True or False

You can set an ALIAS record for an EC2 DNS name.

Answer 4

False! You CAN NOT set an ALIAS record for an EC2 DNS name.

Examples of ALIAS targets are:

• elastic load balancers
• amazon cloudfront
• s3 websites
• amazon API gateway

Question 5

What’s the main difference between CNAME records and ALIAS records?

Answer 5

Alias records can be set for the root domain, eg. example.com

… whereas CNAME records can only be set for subdomains, eg. api.example.com

Question 6

Describe Route 53 routing policies

Answer 6

Routing policies define how Route 53 responds to DNS queries

The routing policies are:

• simple
• weighted
• failover
• latency based
• geolocation
• multi-value answer
• geoproximity

Question 7

Describe weighted routing policy

Answer 7

weighted policy lets you control the percentage of the request that go to each specific resource

eg.
ip 1.2.3.4 gets 70%
ip 4.5.6.7 gets 30%

assigning weight of 0 stops sending traffic to the resource

Question 8

describe the latency based routing policy

Answer 8

redirect to the resource that has the least latency to us

great for applications where low latency is a priority

Question 9

Describe a failover routing policy

Answer 9

Failover routing policy lets you declare a secondary record to use if the primary record’s health check fails

Question 10

describe geolocation routing policy

Answer 10

routing is based on user location - this is different from latency!

specify by continent, country, state, etc

great use cases: website localization, restrict content distribution, load balancing

Question 11

describe geoproximity routing policy

Answer 11

routes traffic to resources based on the geographic location of users and resources

shift more or less traffic to resources based on a defined bias

resources are specified by either AWS region, or latitude and longitude

use case: when you need to shift traffic from one resource to another

Question 12

describe route 53 traffic flow

Answer 12

traffic flow is a visual editor that helps manage complex routing decision trees

these can be saved as traffic flow policies
- supports versioning

Question 13

describe multi-value routing policy

Answer 13

let’s you route traffic to multiple resources (can be based on health checks)

up to 8 healthy records are returned for each multi-value query

think of this as a client-side load balancer

Question 14

You have purchased mycoolcompany.com on Amazon Route 53 Registrar and would like the domain to point to your Elastic Load Balancer my-elb-1234567890.us-west-2.elb.amazonaws.com.

Which Route 53 Record type must you use here?

Answer 14

ALIAS.

CNAME does not support root level domains

Question 15

You have deployed a new Elastic Beanstalk environment and would like to direct 5% of your production traffic to this new environment. This allows you to monitor for CloudWatch metrics and ensuring that there’re no bugs exist with your new environment.

Which Route 53 Record type allows you to do so?

Answer 15

Weighted

Weighted Routing Policy allows you to redirect part of the traffic based on weight (e.g., percentage). It’s a common use case to send part of traffic to a new version of your application.

Question 16

You have updated a Route 53 Record’s myapp.mydomain.com value to point to a new Elastic Load Balancer, but it looks like users are still redirected to the old ELB.

What is a possible cause for this behavior?

Answer 16

Because of the TTL.

Each DNS record has a TTL (Time To Live) which orders clients for how long to cache these values and not overload the DNS Resolver with DNS requests. The TTL value should be set to strike a balance between how long the value should be cached vs. how many requests should go to the DNS Resolver.

Question 17

You have an application that’s hosted in two different AWS Regions us-west-1 and eu-west-2. You want your users to get the best possible user experience by minimizing the response time from application servers to your users.

Which Route 53 Routing Policy should you choose?

Answer 17

Latency.

Latency Routing Policy will evaluate the latency between your users and AWS Regions, and help them get a DNS response that will minimize their latency (e.g. response time)

Question 18

You have a legal requirement that people in any country but France should NOT be able to access your website.

Which Route 53 Routing Policy helps you in achieving this?

Answer 18

Geolocation

Question 19

You have purchased a domain on GoDaddy and would like to use Route 53 as the DNS Service Provider.

What should you do to make this work?

Answer 19

Create a public hosted zone and update the 3rd party registrar NS records

Public Hosted Zones are meant to be used for people requesting your website through the Internet. Finally, NS records must be updated on the 3rd party Registrar.

Question 20

Which of the following are NOT valid Route 53 Health Checks?

a. health check that monitors SQS queue
b. health check that monitors an endpoint
c. health check that monitors other health checks
d. health check that monitors cloudwatch alarms

Answer 20

a. health check that monitors SQS queue