Network - Route53 - DNS 101

Question 1

If you’ve used the Internet…

Answer 1

…you’ve used DNS

Question 2

DNS is used to convert…

Answer 2

…human friendly domain names into an IP address

Question 3

IP addresses are used by…

Answer 3

…computers to identify each other on the network

Question 4

IP address forms

Answer 4

IPv4, IPv6

Question 5

IPv6 was created because…

Answer 5

…we were running out of IPv4 addresses

Question 6

Top Level Domains - example

Answer 6

“.com” in google.com

Question 7

Second word in a domain name

Answer 7

second level domain name

Question 8

Top level domain names controlled by…

Answer 8

…Internet Assigned Numbers Authority (IANA) in a root zone database (DB of all available top level domains)

Question 9

Domain Registrars

Answer 9

ensure that domain names aren’t duplicated. Each domain name becomes registered in a central database known as the WhoIS database

Question 10

SOA Records

Answer 10

Start of Authority Records

Question 11

SOA Record stores information about…

Answer 11

• the name of the server that supplied the data for the zone
• the administrator of the zone (contact details, owner name)
• current version of the data file
• number of seconds a secondary name server should wait before checking for updates
• the number of seconds a secondary name server should wait before retrying a failed zone transfer
• the maximum number of seconds that a secondary name server can use data before it must either be refreshed or expire
• the default number of seconds for the time-to-live file on resource records

Question 12

NS records

Answer 12

stands for Name Server records, used by Top Level Domain servers to direct traffic to the Content DNS server which contains the authoritative DNS records

Question 13

A records

Answer 13

Address Record. A record used by computer to translate the name of the domain to the IP address

Question 14

Do ELBs have an IPv4 or IPv6 address?

Answer 14

No, they have just a DNS name.

Question 15

Can you use an A record to resolve to an ELB?

Answer 15

No, use an Alias Record

Question 16

TTL record

Answer 16

The length that a DNS record is cached on either the Resolving Server or the user’s own local PC is equal to the value of the Time To Live in seconds.

Question 17

The lower the TTL…

Answer 17

…the faster changes to DNS records take to propagate throughout the internet

Question 18

If adding additional A records, servers to production website or migrate production website to AWS…

Answer 18

…DNS change required, will take time to propagate to all end users. Decrease TTL to 300 seconds

Question 19

CNAMES (Canonical Name)

Answer 19

resolve one domain name to another

Question 20

Alias Records

Answer 20

map record resource sets in your hosted zone to ELBs, CloudFront distributions, or S3 buckets that are configured as websites

Question 21

Key difference between CNAMEs and Alias Records

Answer 21

CNAME can’t be used for naked domain names (zone apex). A records or Alias Records can

Question 22

Alias resource record sets can save you time because…

Answer 22

…Route53 automatically recognizes changes in the record sets that the alias resource record set refers to

Question 23

Example of how Alias resource record sets can save you time

Answer 23

Alias resource record set for example.com points to an ELB at lb1-1234.us-east-1.elb.amazonaws.com. If IP of ELB changes, Route53 will reflect those changes in the DNS answers for example.com w/o any changes to the hosted zone that contains resource record sets for example.com

Question 24

Do ELBs have a pre-defined IPv4 address?

Answer 24

No, you resolve to them using a DNS name

Question 25

If you make a request to Route53, CNAMEs…

Answer 25

…will be associated w/ a charge. On the other hand, Alias Records won’t