DNS 101 Flashcards

1
Q

What is DNS

A

It’s the internet’s phone book. It translates URL addresses to IP addresses. For example, http://acloud.guru to 82.124.53.1. In this analogy, the URL address is a business name, and the IP address is their phone number. If you’ve ever seen a phone book…

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2
Q

How many bits in an IPv4 address?

A

32

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3
Q

How many IPv4 addresses can exist?

A

over 4 billion.

4,294,967,296 to be exact.

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4
Q

How many bits in an IPv6 address?

A

128

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5
Q

How many IPv6 addresses can exist?

A

340 undecillion addresses.

That’s 340, followed by 36 zeroes.

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6
Q

What is a Top Level Domain?

A

the last word after the last dot in a domain name

.guru

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7
Q

What is the second level domain?

A

the word before the last dot.

acloud.guru

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8
Q

In this following example, which is top level, and which is the second level?
buystuff.com

A
buystuff = second level
.com = top level
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9
Q

In this following example, which is top level, and which is the second level?
.co.uk

A
.co = second level
.uk = top level
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10
Q

Who manages and controls top level domains?

A

IANA - Internet Assigned Numbers Authority

www.iana.org

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11
Q

What is the name of the database controlled by IANA

A

Root zone database

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12
Q

If you want to see all the available top level domains, where can you go?

A

http://www.iana.org/domains/root/db

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13
Q

what is a domain registrar?

A

An authority that can assign names directly under one or more top-level domains.

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14
Q

Where are domain names registered to?

A

InterNIC, a service of ICANN.

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15
Q

What is ICANN?

A

A service that enforces the uniqueness of domain names across the internet.

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16
Q

What is the database where domain names are registered?

A

The WhoIS database

17
Q

Examples of domain registrars

A

AWS Route 53, GoDaddy, 123-reg-co-uk

18
Q

Each DNS record contains what kind of entry?

A

Start of Authority (SOA)

19
Q

What information is contained in a Start of Authority

A

Name of the server that supplied the zone data
The administrator of the zone
The current version of the zone
the TTL in seconds on resource records

20
Q

What is an NS Record?

A

Used by Top Level domains to direct traffic to the content DNS server which contains the authoritative DNS record

21
Q

What is an A record?

A

The fundamental DNS record that translates the domain name to the IP address.

22
Q

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

A

Address

23
Q

What is a DNS TTL?

A

The length of time the record is cached. The longer the TTL, the longer DNS changes take to propogate.

24
Q

What is a CNAME?

A

Used to resolve one domain name to another.

25
Q

What is an Alias record?

A

Similar to CNAME, an alias is also used to map resource record sets in your hosted zone to Elastic Load Balancer, CloudFront, or S3 web hosting buckets.

26
Q

Can CNAMEs be used for apex records?

A

No

27
Q

True or False: Elastic Load Balancers do not have a predefined IPv4 address?

A

True. You will always resolve to them using the DNS name.

28
Q

Given the choice, should you always choose Alias over CNAME records?

A

Yes.

29
Q

True or False: Alias records save time because changes to the records are recognized automatically without requiring any changes to the hosted zone?

A

True.