Week 4 - Name Resolution

Question 1

What is DNS? What does it do?

Answer 1

Domain Name System

DNS is a global network service that translates a string of letters into an IP address for you

Question 2

What’s a domain name?

Answer 2

Domain names are unique, easy-to-remember letter addresses that can be translated into an IP address by the DNS

Question 3

What is name resolution?

Answer 3

The method of using DNS to look up an IP address associated with a domain name

Question 4

What are 4 things that must be configured for a host to operate on a network?

Answer 4

1. IP address
2. DNS server
3. Router/Gateway
4. Subnet mask

Question 5

What are the 5 primary types of DNS servers?

Answer 5

1. Caching name server
2. Recursive name server
3. Root name server
4. TLD name server
5. Authoritative name server

Question 6

What do the caching name servers do?

Answer 6

They store a local copy of recent DNS lookups

the time it’s stored is based on the data’s TTL

Question 7

What is a TTL in DNS? Every ____ has one

Answer 7

TTL = time to live in seconds

Every domain name has one, and it tells the name server how long to hold onto the name lookup data

Question 8

What do recursive name servers do?

Answer 8

Recursive name servers perform a full address resolution protocol

Question 9

How many root name server authorities are there? How are they distributed?

Answer 9

There are 13 root name server authorities and they are distributed using Anycast

Question 10

What is anycast?

Answer 10

Anycast is a technique used by the name servers to route traffic depending on factors like link health, congestion, and location

Question 11

Describe the steps a local recursive server takes to perform a full address resolution:

Answer 11

1. Computer contacts root name server
2. Root name directs traffic to TLD server
3. TLD responds again with a redirect to the authoritative name server
4. Authoritative name server responds with actual IP address

Question 12

Describe the 5 primary types of DNS servers

Answer 12

1. Caching - stores a local copy of DNS lookups
2. Recursive - full address resolution name lookup
3. Root - provides the name lookup service
4. TLD - provides the last part of a domain and redirects to authoritative
5. Authoritative - the organization that runs the domain, provides the IP address

Question 13

Why is the hierarchical DNS lookup process important?

Answer 13

A computer sends traffic to an IP blindly and the hierarchical DNS lookup process prevents malicious intervention/redirection of traffic

Question 14

What port is reserved for DNS?

Answer 14

DNS uses Port 53

Question 15

What’s the difference between a DNS resolver and a DNS server?

Answer 15

the DNS resolver performs the lookup and resends the request when needed and the DNS server listens for the request of data

Question 16

What is an A record in name resolution?

Answer 16

A single A Record points to a single domain name to a certain IPv4 address

Question 17

What is a DNS Round Robin in name resolution?

Answer 17

repeatedly cycles through a list of items 1 by 1 in order

Question 18

How does DNS Round Robin balance traffic?

Answer 18

DNS Round Robin cycles the separate client’s connection to each A record available in order

Question 19

What is a Quad A record?

Answer 19

Same function as an A record but returns an IPv6 address instead of an IPv4

Question 20

What is the CNAME resource record?

Answer 20

It’s the canonical name for a domain name and redirects traffic to the canonical domain

Question 21

What is the MX resource record and what does it do?

Answer 21

Mail Exchange resource record handles the resolving of email domains

An MX record stores a mail server’s IP.

Question 22

What is the SRV in name resolution?

Answer 22

The service resource record directs traffic to a specific service using its port

Question 23

What is TXT and what is it used for?

Answer 23

It stores any additional information

Question 24

What is ICANN? What do they do?

Answer 24

ICANN is the Internet Corporation for Assigned Names and Numbers

They distribute TLDs

Question 25

What are the 3 parts of a domain?

Answer 25

1. TLD .com, .org, .net
2. domain google, youtube, twitch
3. subdomain www.

Question 26

What do you call all parts of a domain combined?

Answer 26

FQDN

Fully qualified domain name

Question 27

What is a registrar?

Answer 27

a registrar is a company that works in accordance with ICANN to sell unregistered domain names

Question 28

What’s the purpose of DNS zones?

Answer 28

DNS zones allow easier control over multiple levels of a domain

Question 29

What are zone files? What 2 files does it contain?

Answer 29

Zone files declare all resource records for a zone and contain:

• SOA files (start of authority)
• NS files

Question 30

What is SOA? Where do you find this?

Answer 30

Start of Authority

they are in zone files and indicate the zone and which name server is authoritative of it

Question 31

What are NS records? Where are they found?

Answer 31

names other servers that might be in charge of the zone

they are found in zone files

Question 32

What do reverse lookup zone files do?

Answer 32

Reverse lookup zone files let DNS resolvers ask for an IP and also provide the FQDN associated

Question 33

What is a PTR?

Answer 33

pointer record

resolve an IP address to a name