DNS

Question 1

Domain Name System

DNS

Answer 1

A service that resolves fully qualified domain names (FQDNs) to IP addresses and IP addresses to FQDNs.

Question 2

. (dot) Domain

Answer 2

The root domain, or root of the DNS domain tree, denotes a fully qualified unambiguous domain name.

Question 3

Fully Qualified Domain Names

FQDN

Answer 3

The FQDN includes the host name and all domain names separated by periods. The final period, which is for the root domain, is normally omitted and only implied.

Question 4

Top-Level Domain

TDL

Answer 4

Sometimes known as a first-level domain, a TDL is the last part of a domain name (.com, .edu, .gov). TDLs are managed by the Internet Corporation of Assigned Names and Numbers (ICANN).

Question 5

Second-Level Domain

Answer 5

Additional domains, or second-level domains, are registered to an individual or organization for use on the internet. Comes right before the “.com” in a domain.

Question 6

Third-Level Domain

Answer 6

Third-level domains are only used in the United Kingdom (UK) and are associated with the co.uk first- and second-level name domains. Third-level domains are registered to individuals or organizations for use on the internet in the same way second-level domains are registered in the rest of the world. An example of a third-level domain in the DNS domain tree is bbc.co.uk.

Question 7

Hostname

Answer 7

The hostname is the part of a FQDN that represents a specific host. It is the left-most name in an FQDN. For example, “www” is the hostname of www.example.com.

Question 8

Sub-Domain

Answer 8

In an FQDN, any domain between the hostname and the second-level domain is a sub-domain. Sub-domains are not registered. Responsibility for sub-domains lies with the individual or organization that registered the second-level domain. Docs.microsoft.com and news.google.com are examples of sub-domains in the DNS domain tree.

Question 9

DNS Client

Answer 9

A client computer that is configured to send name resolution queries to a DNS server.

Question 10

DNS Client Cache

DNS Resolver Cache

Answer 10

A temporary database maintained by the DNS client that contains previously resolved FQDNs and their matching IP addresses.

Question 11

Host File

Answer 11

A plain text file that maps FQDNs to IP addresses.

Question 12

DNS Server

Answer 12

A type of name server that responds to DNS queries using a database of hostnames and their associated records.

Question 13

DNS Server Cache

Answer 13

A temporary database maintained by the DNS server that contains previously resolved FQDNs and their matching IP addresses.

Question 14

Authoritative DNS

Answer 14

A DNS server that holds original and definitive DNS records for the domains it is responsible for.

Question 15

DNS Forwarding

Answer 15

Occurs when one DNS server queries another DNS server when it can’t resolve a FQDN.

Question 16

Conditional Forwarding

Answer 16

Occurs when a DNS server forwards queries for certain DNS domains to certain DNS servers.

Question 17

Stub Zone

Answer 17

A DNS zone containing a list of authoritative DNS servers for a specific DNS domain.

Question 18

Root Hints

Answer 18

The process of resolving FQDNs by first contacting root DNS servers followed by contacting delegated DNS servers.

Question 19

Delegation

Answer 19

The process of responding to DNS queries by delegating to a DNS server that is lower in the DNS tree, but closer to the requested FQDN.

Question 20

ipconfig /displaydns

Answer 20

Displays records in the DNS client cache, which includes both entries preloaded from the local Hosts file and any recently obtained resource records from a DNS server.

Question 21

ipconfig /flushdns

Answer 21

Displays records in the DNS client cache, which includes both entries preloaded from the local Hosts file and any recently obtained resource records from a DNS server.