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DNS 101 > DNS 101 > Flashcards

DNS 101 Flashcards

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1
Q

DNS stands for

A

Domain name system

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2
Q

Naming of Route53

A

because DNS is using Port 53

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3
Q

DNS is used to

A

convert human friendly domain names into an IP address

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4
Q

IP addresses are used by computers to

A

identify each other on the network

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5
Q

IP addresses come in 2 different forms

A
  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)

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6
Q

TLD

A

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

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7
Q

Second level domain ex

A

.co.uk, .gov.uk

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8
Q

TLDs are controlled by

A

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

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9
Q

Domain Registrar

A

> 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

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10
Q

WhoIS DB

A

a central DB that has all registered domain names

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11
Q

Popular domain registrars

A

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

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12
Q

SOA

A

Start of Authority Record

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13
Q

SOA record stores info about

A
  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
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14
Q

NS

A

Name Server Records

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15
Q

NS are used by

A

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

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16
Q

Browser to SOA sequence of steps

A
  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
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17
Q

A Record

A
  1. Fundamental type of DNS record.

2. “A” for Address

18
Q

A record is used

A

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

19
Q

TTL

A

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

20
Q

TTL change propagation

A

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

21
Q

Default TTL for most providers

A

48 hours

22
Q

CNAME

A

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

23
Q

Example of CNAME

A

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

24
Q

Alias records are used to

A

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

25
Q

Key difference between Alias and CNAME

A

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

26
Q

How do you resolved to ELBS

A

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

27
Q

Common DNS Types

A
  1. SOA Records
  2. NS Records
  3. A Records
  4. CNAMES
  5. MX Records
  6. PTR Records
28
Q

MX Records

A

used for mail; mail exchanger record

29
Q

PTR

A

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

30
Q

Routing policies available in Route53

A
  1. Simple
  2. Weighted
  3. Latency-Based
  4. Failover
  5. Geolocation
  6. Geoproximity Routing (Traffic Flow Only)
  7. Multivalue Answer Routing
31
Q

Simple Routing Policy

A
  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)
32
Q

Weighted Routing Policy

A
  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
33
Q

Health Check can be set at

A

individual record sets

34
Q

Alerting for health checks

A

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

35
Q

Latency-Based Policy

A
  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)
36
Q

Failover Routing Policy

A
  1. Used when you want to create an active/passive setup
37
Q

Geolocation Routing Policy

A

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

38
Q

Geoproximity Routing (Traffic Flow Only)

A
  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
39
Q

BIAS

A

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

40
Q

What needs to be used for geoproximity routing

A

use Route53 Traffic flow

41
Q

Multivalue Answer Policy

A

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

DNS 101 (1 decks)

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