Route 53

Question 1

What are the DNS Terminologies?

Answer 1

• Domain Registrar: Amazon Route 53, GoDaddy, …
• DNS Records: A, AAAA, CNAME, NS, …
• Zone File: contains DNS records
• Name Server: resolves DNS queries (Authoritative or Non-Authoritative)
• Top Level Domain (TLD): .com, .us, .in, .gov, .org, …
• Second Level Domain (SLD): amazon.com, google.com, …

Question 2

How does DNS works?

Answer 2

local dns - root dns - tld dns - sld dns server

Question 3

What is Amazon Route 53?

Answer 3

A highly available, scalable, fully managed and Authoritative DNS, also a Domain Registar.

Question 4

Can Route53 check the health of resources?

Answer 4

yes it can

Question 5

Whats the availabilty of R53?

Answer 5

100%

Question 6

What are in a R53 Record?

Answer 6

• Domain/subdomain Name – e.g., example.com
• Record Type – e.g., A or AAAA
• Value – e.g., 12.34.56.78
• Routing Policy – how Route 53 responds to queries
• TTL – amount of time the record cached at DNS Resolvers

Question 7

What are the R53 supported records?

Answer 7

• (must know) A / AAAA / CNAME / NS
• (advanced) CAA / DS / MX / NAPTR / PTR / SOA / TXT / SPF / SRV

Question 8

What is an A record?

Answer 8

A – maps a hostname to IPv4

Question 9

What is an AAAA record?

Answer 9

AAAA – maps a hostname to IPv6

Question 10

What is an CNAME record?

Answer 10

• CNAME – maps a hostname to another hostname
• The target is a domain name which must have an A or AAAA record
• 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

Question 11

What is a NS record?

Answer 11

• NS – Name Servers for the Hosted Zone

Question 12

Whate types of Hosted Zones are in R53?

Answer 12

• Public Hosted Zones – contains records that specify how to route
  traffic on the Internet (public domain names)
  application1.mypublicdomain.com
• Private Hosted Zones – contain records that specify how you route
  traffic within one or more VPCs (private domain names)
  application1.company.internal

Question 13

Do you have to pay for Hosted Zones

Answer 13

Yes, $0.5 per month per zone

Question 14

What is TTL?

Answer 14

It stands for Time to live. Defines the cache time for a record.
* High ttl - less traffic, can be outdated
* Low ttl - more cost, easy to change record

Question 15

Is TTL mandatory?

Answer 15

Yes it is except for Alias records.

Question 16

Whats the difference between CNAME and Alias?

Answer 16

*CNAME: points a hostname to another hostname, ONLY FOR NON ROOT DOMIAN
* Alias: points a hostname to an AWS Resource, root and non root domains, free, native health checks

Question 17

Whats the type of the Alias record?

Answer 17

It A/AAAAl.

Question 18

What can be the target of the Alias record?

Answer 18

• 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 CANT SET ALIAS FOR AN EC2 DNS name

Question 19

What are R53 Routing Policies?

Answer 19

Define how Route 53 responds to DNS queries.

Question 20

What are the supported R53 policies?

Answer 20

• Simple
• Weighted
• Failover
• Latency based
• Geolocation
• Multi-Value Answer
• Geoproximity (using Route 53 Traffic Flow feature)

Question 21

What is a simple R53 policy?

Answer 21

• Typically, route traffic to a single resource
• Can specify multiple values in the same record
• If multiple values are returned, a RANDOMone is chosen by the client
• CAN’T be associated with health checks

Question 22

What is a Weighted R53 policy?

Answer 22

• Control the % of the requests that go to each specific resource
• DNS records must have the same name and type
  Can be associated with Health Checks
• Use cases: load balancing between regions, testing new application versions…
• Assign a weight of 0 to a record to stop sending traffic to a resource
• If all records have weight of 0, then all records will be returned equally

Question 23

What is a Latency-based R53 policy?

Answer 23

• Redirect to the res. that has the least latency close to us
• Latency is based on traffic between user and AWS Regions
• Can be ass. with health checks

Question 24

What are R53 Health Checks?

Answer 24

• HTTP Health Checks are only for public resources
• Health Check => Automated DNS Failover:
  1. Health checks that monitor an endpoint (application, server, other AWS resource)
  2. Health checks that monitor other health checks (Calculated Health Checks)
  3. Health checks that monitor CloudWatch Alarms (full control !!) – e.g., throttles of DynamoDB, alarms on RDS, custom metrics,
• Health Checks are integrated with CW metrics

Question 25

How does Monitor an endpoint work?

Answer 25

* About 15 global health checkers will check the endpoint health * Health Checks pass only when the endpoint responds with the 2xx and 3xx status codes * Health Checks can be setup to pass / fail based on the text in the first 5120 bytes of the response * Configure you router/firewall to allow incoming requests from Route 53 Health Checkers

Question 26

How does Calcualted Health Check work?

Answer 26

* Combine the results of multiple Health Checks into a single Health Check * You can use OR, AND, or NOT * Can monitor up to 256 Child Health Checks

Question 27

How to Health Check Private Hosted Zones?

Answer 27

You can create a CloudWatch Metric and associate a CloudWatch Alarm, then create a Health Check that checks the alarm itself.

Question 28

How does Failover policy work?

Answer 28

You have to setup a Primary and a Secondary endpoint and it will automatically roll over if the primary is Unhealthy.

Question 29

What is Geolocation policy, how does it work?

Answer 29

* This routing is based on user location * Specify location by Continent, Country or by US State (if there’s overlapping, most precise location selected) * Should create a “Default” record (in case there’s no match on location) * Can be associated with health checks

Question 30

How does Geoproximity policy work?

Answer 30

* Route traffic to your resources based on the geographic location of users and resources * Ability to shift more traffic to resources based on the defined bias * To change the size of the geographic region, specify bias values * You must use the R53 Traffic Flow feature

Question 31

What is IP-based routing policy?

Answer 31

* Routing is based on clients’ IP addresses * You provide a list of CIDRs for your clients and the corresponding endpoints/locations (user-IP-to-endpoint mappings) * Example: route end users from a particular ISP to a specific endpoint

Question 32

What is the Multi-Value policy?

Answer 32

* Use when routing traffic to multiple resources * Can be assigned with Health Checks * Up to 8 healthy records are returned for each query * Client choose randomly

Question 33

Can you use a domain name that wasn't bought in Amazon Registar?

Answer 33

Yes you can, but you have to set the R53 dns servers in the 3rd party provider site.