DNS / Route 53

Question 1

How are top level domain names controlled?

Answer 1

They are controlled by IANA in a root zone database, which is a database of all available top level domains.

Question 2

What is the key purpose of domain registrars?

Answer 2

Ensuring that all names in a given domain are unique.

Question 3

What does SOA stand for?

Answer 3

Start Of Authority Record

Question 4

What info is contained in an SOA?

Answer 4

• The name of the server that supplied data for the zone
• Administrator of the zone
• Current version of the data file
• default # of seconds for the TTL file on resource records

Question 5

What does NS stand for?

Answer 5

Name Server Records

Question 6

What is the purpose of an NS Record?

Answer 6

They are used by Top Level Domain servers to direct traffic to the Content DNS server which contains the authoritative DNS records.

Question 7

What does the “A” stand for in “A” Record?

Answer 7

Address

Question 8

What does an “A” Record do?

Answer 8

The A record is used by the computer to translate the name of the domain to an IP address

Question 9

In the context of DNS, why is TTL important?

Answer 9

• TTL is the length of time that a DNS record is cached on either the Resolving Server or the user’s own local PC.
• The lower the TTL, the faster changes to DNS records take to propogate throughout the internet.

Question 10

What does CName stand for?

Answer 10

Canonical Name

Question 11

What does a CName do?

Answer 11

A CNAME is used to resolve one domain name to another

(Imagine looking in the phone book for BATMAN -> See West, Adam)

Question 12

What is an Alias Record?

Answer 12

Alias Records are used to map resource record sets in your hosted zone to Elastic Load Balancers, CloudFront Distributions, or S3 buckets that are configured as websites.

Question 13

What is a naked domain name?

Answer 13

a DNS server name that doesn’t have the “www” or any other subdomains

Question 14

What is a zone apex record?

Answer 14

A DNS name that doesn’t have “www” or any of the other subdomains

Question 15

What is the key difference between an Alias Record and a CName?

Answer 15

While both are used to map a DNS name to another, CNames cannot be used for naked domain names

Question 16

Do Elastic Load Balances have pre-defined IPv4 addresses?

Answer 16

No, you resolve to them using a DNS name

Question 17

On the exam, given the choice between an Alias Record and a CName, which should you pick?

Answer 17

Alias Records (CNAMEs can’t handle zone apex records)

Question 18

What does the MX stand for in MX Record?

Answer 18

Mail Exchanger

Question 19

What does the PTR stand for in PTR Record?

Answer 19

Pointer

Question 20

At a high level, what does a PTR Record do?

Answer 20

Maps an IP address to a domain/host name

(Think inverse of an A record)

Question 21

Can you buy domain names directly from AWS?

Answer 21

Yes, but it can take up to 3 days to register depending on the circumstances.

Question 22

What are the common DNS types?

Answer 22

• SOA Records
• NS Records
• A Records
• CNAMES
• MX Records
• PTR Records

Question 23

What is the limit to the number of domain names you can manage using Route53?

Answer 23

default limit is 50 domain names, but this can be increased by contacting AWS Support

Question 24

Can an Alias record point to AWS Resources that are hosted in other accounts?

Answer 24

Yes, by manually entering the ARN

Question 25

There is a website hosted in AWS that might get a lot of traffic over the next few weeks. If the application experiences a natural disaster at this time, what should be done to reduce potential disruption to users?

Answer 25

Use Route53 to route requests to another instance in a different region