4.7 DNS

Question 1

What is a forward lookup address

Answer 1

finds the IP address for a given host name

Question 2

What is a revers lookup

Answer 2

finds the host name from a given IP address.

Question 3

What is a root dns server

Answer 3

hold information for the root zone (.). Root servers answer name resolution requests by supplying the address of the corresponding top-level DNS server

Question 4

. (dot) domain

Answer 4

The . (dot) domain, the root domain, denotes a fully qualified, unambiguous domain name.

Question 5

Top-Level Domain (TLD)

Answer 5

A TLD is the last part of a domain name (for example, .com, .edu, .gov). TLDs are managed by the Internet Corporation of Assigned Names and Numbers (ICANN).

Question 6

Fully Qualified Domain Name (FQDN)

Answer 6

The FQDN includes the host name and all domain names separated by periods. The final period (which is for the root domain) is often omitted and implied.

Question 7

Additional domains
(Second-level domains)

Answer 7

Additional domains are second-level domains that have names registered to an individual or organization for use on the internet.

Question 8

Host Name

Answer 8

The host name is the part of a domain name that represents a specific host. For example, www is the host name of www.example.com.

Question 9

Records

Answer 9

are used to store entries for host names, IP addresses, and other information in the zone database.

Question 10

Authoritative Server

Answer 10

An authoritative server is a DNS server that has a complete copy of all the records for a particular domain.

Question 11

Dynamic DNS (DDNS)

Answer 11

DDNS enables clients or the DHCP server to update records in the zone database. Without dynamic updates, all A (host) and PTR (pointer) records must be configured manually.

Question 12

What is recursion?

Answer 12

the process by which a DNS server uses root name servers and other DNS servers to perform name resolution.

Question 13

What is the first step in recursion

Answer 13

The host looks in its local cache to see if it has recently resolved the host name.

Question 14

What is the second step in recursion

Answer 14

If the information is not in the cache, it checks the Hosts file. The Hosts file is a static text file that contains host-name-to-IP address mappings.

Question 15

What is the third step in recursion?

Answer 15

If the IP address is not found, the host contacts its preferred DNS server. If the preferred DNS server can’t be contacted, the host continues contacting additional DNS servers until one responds.

Question 16

What is the fourth step in recursion

Answer 16

The host sends the name information to the DNS server. The DNS server checks its cache and Hosts file. If the information is not found, the DNS server checks any zone files that it holds for the requested name.

Question 17

What is the fifth step in recursion

Answer 17

If the DNS server can’t find the name in its zones, it forwards the request to a root zone name server. This server returns the IP address of a DNS server that has information for the corresponding top-level domain (such as .com).

Question 18

what is the sixth step in recursion

Answer 18

The first DNS server requests the information from the top-level domain server. The server returns the address of a DNS server with the information for the next highest domain. This process continues until a DNS server is contacted that holds the necessary information.

Question 19

What is the seventh step in recursion

Answer 19

The DNS server places the information in its cache and returns the IP address to the client host. The client host also places the information in its cache and uses the IP address to contact the desired destination device.

Question 20

router(config)#ip host [name] a.b.c.d

Answer 20

Creates static DNS entries.

Question 21

router(config)#ip domain-name [name]

Answer 21

Configures the router default domain (for DNS).

Question 22

router(config)#ip name-server a.b.c.d

Answer 22

Sets the default DNS name server.

Question 23

router(config)#ip domain-lookup

Answer 23

Enables the router to use DNS to identify IP addresses from hostnames.

Question 24

router(config)#no ip domain-lookup

Answer 24

Disables the broadcast name resolution of hostnames.

Question 25

router#show hosts

Answer 25

Displays a list of known IP hosts.

Question 26

Where does a Device Details Router or Switch DNS name resolution looks for information and in what order

Answer 26

Static DNS entries

DNS server query (if enabled)

Question 27

Where does a Workstation DNS name resolution looks for information and in what order

Answer 27

Local DNS cache
HOSTS file
DNS server query (Primary)
DNS server query (Secondary)