DNS

Question 1

What is the difference between Iterative and Recursive DNS servers?

Answer 1

With iterative servers, the client is responsible for querying all levels of DNS servers by itself whereas recursive servers do the job on behalf of the client.
DNS Resolvers are recursive in nature.

Question 2

What is FQDN?

Answer 2

protocol://sub-domain.domain-name.top-level-domain
E.G. https://www.google.com

Question 3

What are the four levels of DNS servers?

Answer 3

Authoritative Name servers
TLD Server
Root Servers
DNS Resolvers (recursive)

Question 4

List two commands to resolve domain names.

Answer 4

dig (Linux)
nslookup (Windows)

Question 5

How do you check if the DNS resolution coming from the cache?

Answer 5

dig (in Linux)
TTL is provided; Query Time: 0 msec

Question 6

List the names of two DNS resolvers and their IP.

Answer 6

Cloudflare (1.1.1.1)
Google (8.8.8.8, 8.8.4.4)

Question 7

How many Root Servers are there across the globe?

Answer 7

13 servers across the globe maintained by InterNIC

Question 8

What is the typical caching time for DNS queries in the client?
What is the advantage of having low TTL?

Answer 8

5 - 15 mins (depending on the domain)
Low TTL is needed for HA

Question 9

Which service in AWS responsible for DNS?

Answer 9

Route 53

Question 10

Can DNS servers facilitate client-side load balancing?

Answer 10

By providing multiple values (i.e. IPs) in the response

Question 11

How would you locate the nearest DNS server to reduce the response time of DNS queries?

Answer 11

Using Anycast Routing
(8.8.8.8 & 1.1.1.1 are Anycast IP)

Question 12

What is GeoDNS or GeoLocation Routing(AWS)?

Answer 12

DNS servers check the location of the user based on request’s IP and respond with server IP nearest to the client.

Question 13

What are the three methods to prevent evesdropping of data by your company?

Answer 13

Use split tunnel in VPN. Traffic for routes are not pushed by company won’t go to corporate network. However, company will force to use their DNS servers and log browsing history.

Use VPN server to encrypt your data but company can still log browsing history as DNS is over http.

In Browser enable, DNS over HTTPS. However, company will manage browser and will disable this option.

Last option, disconnect VPN and then work. However, Yashika’s company controls that too. Legacy vendors have a solution.

Use your own laptop BYOD but that might not be allowed by company

Use TOR browser however it might be blocked by someone