Domain Name Service - Quiz Explanation

The answers you selected are indicated below, along with text that explains the correct answers.

1.	What is the purpose of the top-level subdomains? Please select the best answer.
	A.	To convert domain names into IP addresses
	B.	To contain all hosts belonging to organizations of particular types
	C.	To distribute information among many different machines on the Internet
	D.	To provide the Fully Qualified Domain Name (FQDN) of a DNS entity
	The correct answer is B. The current top-level subdomains are: .com, for commercial organizations; .edu, for educational institutions; .gov, for civilian government organizations; .mil, for military organizations, .net for network support centers; and .org for such organizations as non-profits, lobbying groups, and so on.

2.	What is a name server? Please select the best answer.
	A.	A branch of the DNS namespace under the administrative control of some entity
	B.	The primary server which has the official or authoritative information on its zone
	C.	A process that accepts queries into the DNS database, or the computer on which this process runs
	D.	A secondary server providing an alternative source for information on the zone
	The correct answer is C. The name server process binds to UDP and TCP on well-known port 53.

3.	What distinguishes a primary server? Please select the best answer.
	A.	DNS data for a primary server’s zone is stored on the server host’s local disk in zone files.
	B.	A primary server allows for load distribution and provides backup service.
	C.	Only 12 primary servers exist and they are maintained by the InterNIC.
	D.	Primary servers obtain their data from the authoritative server by periodically downloading copies of the zone files.
	The correct answer is A. Every zone needs exactly one associated primary name server to store the official or authoritative information on its zone.

4.	What is the purpose of the Canonical Name (CNAME) Resource Record type? Please select the best answer.
	A.	To set basic parameters for a zone and establish responsible parties
	B.	To declare a name server for a zone
	C.	To specify an address-to-name mapping
	D.	To define an alias for a host
	The correct answer is D. SOA records set the basic parameters for a zone. NS records declare a name server for a zone. P records specify an address-to-name mapping.

5.	What is the purpose of the Pointer (PTR) Resource Record type? Please select the best answer.
	A.	To set basic parameters for a zone and establish responsible parties
	B.	To declare a name server for the zone
	C.	To specify an address-to-name mapping
	D.	To define an alias for a host
	The correct answer is C. Along with Address records, Pointer records are the heart of the DNS database. Address records appear in the forward lookup zone file, and Pointer records appear in the reverse file.

6.	What is the purpose of the Host Information (HINFO) Resource Record type? Please select the best answer.
	A.	To specify an address-to-host name mapping
	B.	To define an alias for a host
	C.	To give the operating system and architecture for the specified host
	D.	To declare a machine to be a name server for a specified zone
	The correct answer is C. Many sites do not put this information into their DNS databases because it may provide information to hackers.

7.	What role do root servers play? Please select the best answer.
	A.	They provide alternative sources for information on a zone.
	B.	They bind together the DNS database through recursion.
	C.	They accept queries into the DNS database.
	D.	They contain the official or authoritative information for a zone.
	The correct answer is B. The twelve root servers are named A.ROOT-SERVERS.NET, B.ROOT-SERVERS.NET, and so on.

8.	Through what process is the distributed DNS database bound together? Please select the best answer.
	A.	Recursion
	B.	Reverse lookup
	C.	Subnetting
	D.	System calls
	The correct answer is A. When a name server receives a query it cannot directly answer, it generates a query of a name server higher in the DNS hierarchy. Reverse lookup is a way to find a host’s name by using that host’s numeric IP address. Subnetting refers to an addressing scheme in which part of the host part of an address is used to extend the network portion of an address.