DNS 101

Question 1

DNS stands for

Answer 1

Domain name system

Question 2

Naming of Route53

Answer 2

because DNS is using Port 53

Question 3

DNS is used to

Answer 3

convert human friendly domain names into an IP address

Question 4

IP addresses are used by computers to

Answer 4

identify each other on the network

Question 5

IP addresses come in 2 different forms

Answer 5

1. IPv4 - 32 bit field (4B diff addresses)

2. IPv6 - created to solve the depletion issue for IPv4 and has an address space of 128bits (34 undecillion address)

Question 6

TLD

Answer 6

Top Level domain; .com, .edu, .gov etc

Question 7

Second level domain ex

Answer 7

.co.uk, .gov.uk

Question 8

TLDs are controlled by

Answer 8

Internet Assigned Numbers Authority (IANA) - root zone database of all top level domains

Question 9

Domain Registrar

Answer 9

> authority that can assign domain names directly under one or more top level domains
these domains are registered with InterNIC, a service of ICANN, which enforces uniqueness of domain names across the internet

Question 10

WhoIS DB

Answer 10

a central DB that has all registered domain names

Question 11

Popular domain registrars

Answer 11

Amazon, GoDaddy.com, 123-reg.co.uk

Question 12

SOA

Answer 12

Start of Authority Record

Question 13

SOA record stores info about

Answer 13

1. name of the server that supplied the data for the zone
2. Admin of the zone
3. current version of the data file
4. default number of seconds for the TTL file on resource records

Question 14

NS

Answer 14

Name Server Records

Question 15

NS are used by

Answer 15

TLD servers to direct traffic to the Content DNS server which contains the authoritative DNS records

Question 16

Browser to SOA sequence of steps

Answer 16

1. Browser doesn’t know the IP address of the hellocloudgurus2019.com
2. Browser goes to the top level domain, it’s querying for the authoritative dns record.
   Ø I have this hellocloudgurus.com, I need to know the ip address for it
   Ø TLD doesn’t contain the IP addresses - it only has hellocloudgurus2019.com 172800 IN NS ns.awsdns.com
3. Once you have the NS info, it queries the NS Records
4. NS records will then give us the SOA
5. In the SOA, that’s where we’ll have our DNS records

Question 17

A Record

Answer 17

1. Fundamental type of DNS record.

2. “A” for Address

Question 18

A record is used

Answer 18

by a computer to translate the name of the domain to an IP address;
ex: www.acloudguru.com might point to http://123.10.10.80

Question 19

TTL

Answer 19

Time to live - length in seconds that a DNS record is cached on either the Resolving server or the users own local PC

Question 20

TTL change propagation

Answer 20

the lower TTL, the faster changes to DNS records take to propagate throughout the internet

Question 21

Default TTL for most providers

Answer 21

48 hours

Question 22

CNAME

Answer 22

Canonical Name - can be used to resolve one domain name to another

Question 23

Example of CNAME

Answer 23

http://m.acloud.guru is using the same address for mobile.acloud.guru (batman see West Adam)

Question 24

Alias records are used to

Answer 24

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

Question 25

Key difference between Alias and CNAME

Answer 25

CNAME can't be used for naked domain names (zone apex record), you can't have a cname for http://acloud.guru, it must be either an A record or an Alias

Question 26

How do you resolved to ELBS

Answer 26

using DNS names, they don't have pre-defined IPv4 addresses

Question 27

Common DNS Types

Answer 27

1. SOA Records 2. NS Records 3. A Records 4. CNAMES 5. MX Records 6. PTR Records

Question 28

MX Records

Answer 28

used for mail; mail exchanger record

Question 29

PTR

Answer 29

reverse of an A record - looking up a name using an IP Address

Question 30

Routing policies available in Route53

Answer 30

1. Simple 2. Weighted 3. Latency-Based 4. Failover 5. Geolocation 6. Geoproximity Routing (Traffic Flow Only) 7. Multivalue Answer Routing

Question 31

Simple Routing Policy

Answer 31

1. you can only have one record with multiple IP addresses 2. If you specify multiple values, Route%3 returns all values to the user in a random order (no health checking unlike the Multivalue Answer Routing)

Question 32

Weighted Routing Policy

Answer 32

1. Allows you to split traffic based on different weights assigned. 2. If a record set fails a health check it will be removed from Route53 until it passes the health check

Question 33

Health Check can be set at

Answer 33

individual record sets

Question 34

Alerting for health checks

Answer 34

SNS can be used to alert you if a health check has failed

Question 35

Latency-Based Policy

Answer 35

1. Allows you to route your traffic based on the lowest network latency for your end user (which region will give them the fastest response time)

Question 36

Failover Routing Policy

Answer 36

1. Used when you want to create an active/passive setup

Question 37

Geolocation Routing Policy

Answer 37

Lets you choose where your traffic will be sent based on the geographic location of your users

Question 38

Geoproximity Routing (Traffic Flow Only)

Answer 38

1. lets Amazon Route 53 route traffic to your resources based on the geographic location of your users and your resources 2. Optionally choose to route more/less traffic to a given resource by specifying a value known as BIAS

Question 39

BIAS

Answer 39

expands or shrinks the size of the geographic region from which traffic is routed to a resource

Question 40

What needs to be used for geoproximity routing

Answer 40

use Route53 Traffic flow

Question 41

Multivalue Answer Policy

Answer 41

lets you configure Amazon Route 53 to return multiple values, such as IP addresses for your web servers, in response to DNS queries; like simple routing except that it checks the health of the each resource - it only returns the healthy ones