CNIT 342 EXAM 2 REVIEW - DNS AND PACKET
FILTERING QUESTIONS WITH VERIFIED ANSWERS
What is the purpose of name resolution? - Answers - - map station names back to IP
addresses
- utilizes hosts files
What is DNS? - Answers - - domain name system (IETF standard)
- hierarchical naming system
True/False: DNS is traditionally a static approach. - Answers - true
- hard-coded list of names and IP address
- assumes station always has same IP
- does NOT work well with DHCP
Describe the DNS name space structure. - Answers -
host.subdomain(s).top_level_domain
- each level unique to next higher level
Up to how many levels of domains are allowed? - Answers - 127 levels (separated by
dots)
Up to how many characters per domain are allowed? - Answers - 63 characters
In which direction is authority handed down in the DNS name space structure? -
Answers - - authority is handed down from top-level to lower levels
Which organization manages the top-level (root) domains? - Answers - - InterNIC
What are some examples of top-level (root) domains managed by InterNIC? - Answers -
.edu, .com, .gov, .mil, .org, country codes, .biz, .info, .name, .pro, .aero, .coop, .museum
Who holds the authority over lower-level domains and all created sub-domains? -
Answers - - holder of a second level domain
- sub-domains can be created at will
What differentiates a domain from a zone? - Answers - - domains map back to names
used in DNS hierarchy (purdue.edu, net.lcl)
- zones represent the METHOD used to manage domains
What is the purpose of a zone? - Answers - - represents the method used to manage
domains
- zones are authoritative for a domain or sub-domain
, - sub-domains can be given their own zone or stored within a single zone
At least how many authoritative DNS servers must each second-level domain have? -
Answers - - at least two authoritative DNS servers
What is an authoritative DNS server? - Answers - - contains the actual DNS entries
- must be up 24/7
- address for server listed in next higher level's configuration
- root server must know about all second-level domain servers
How many root name servers are spread around the world? - Answers - - 13
- named a, b, c....
Describe the forward name resolution process. - Answers - example:
- end node (resolver) in tech.purdue.edu domain asks the local Purdue DNS server for
IP address for www.slashdot.org
- called a recursive query
- name server is obligated to supply an answer
- the local name server isn't authoritative for slashdot.org to it goes and finds the answer
from an authoritative name (consults root hints file, asks .org root server)
- root server is only obligated to point local name server in right direction (lowers load on
root server)
- root server points local server to authoritative server for slashdot.org
- local name server contacts slashdot.org and asks for answer
- slashdot.org server IS authoritative, so it responds with answer
- local name server replies to originative node (resolver)
What is a recursive DNS query? - Answers - - when an end node asks a local DNS
server for the IP address for a domain
What is an iterative query? - Answers - - when a name server isn't authoritative for a
domain and must go and find the answer from an authoritative name (by consulting the
root hints file)
What is DNS caching? - Answers - - resolved names are cached by name servers
- subsequent queries use the cached information
True/False: The amount of time information remains cache is not important in DNS
caching. - Answers - False
- must be a limit or else we could never mode servers
The amount of time that a server can hold cached data is determined by the entry's
what? - Answers - - time to live, TTL
Who is responsible for setting the time to live, TTL? - Answers - - zone administrator
FILTERING QUESTIONS WITH VERIFIED ANSWERS
What is the purpose of name resolution? - Answers - - map station names back to IP
addresses
- utilizes hosts files
What is DNS? - Answers - - domain name system (IETF standard)
- hierarchical naming system
True/False: DNS is traditionally a static approach. - Answers - true
- hard-coded list of names and IP address
- assumes station always has same IP
- does NOT work well with DHCP
Describe the DNS name space structure. - Answers -
host.subdomain(s).top_level_domain
- each level unique to next higher level
Up to how many levels of domains are allowed? - Answers - 127 levels (separated by
dots)
Up to how many characters per domain are allowed? - Answers - 63 characters
In which direction is authority handed down in the DNS name space structure? -
Answers - - authority is handed down from top-level to lower levels
Which organization manages the top-level (root) domains? - Answers - - InterNIC
What are some examples of top-level (root) domains managed by InterNIC? - Answers -
.edu, .com, .gov, .mil, .org, country codes, .biz, .info, .name, .pro, .aero, .coop, .museum
Who holds the authority over lower-level domains and all created sub-domains? -
Answers - - holder of a second level domain
- sub-domains can be created at will
What differentiates a domain from a zone? - Answers - - domains map back to names
used in DNS hierarchy (purdue.edu, net.lcl)
- zones represent the METHOD used to manage domains
What is the purpose of a zone? - Answers - - represents the method used to manage
domains
- zones are authoritative for a domain or sub-domain
, - sub-domains can be given their own zone or stored within a single zone
At least how many authoritative DNS servers must each second-level domain have? -
Answers - - at least two authoritative DNS servers
What is an authoritative DNS server? - Answers - - contains the actual DNS entries
- must be up 24/7
- address for server listed in next higher level's configuration
- root server must know about all second-level domain servers
How many root name servers are spread around the world? - Answers - - 13
- named a, b, c....
Describe the forward name resolution process. - Answers - example:
- end node (resolver) in tech.purdue.edu domain asks the local Purdue DNS server for
IP address for www.slashdot.org
- called a recursive query
- name server is obligated to supply an answer
- the local name server isn't authoritative for slashdot.org to it goes and finds the answer
from an authoritative name (consults root hints file, asks .org root server)
- root server is only obligated to point local name server in right direction (lowers load on
root server)
- root server points local server to authoritative server for slashdot.org
- local name server contacts slashdot.org and asks for answer
- slashdot.org server IS authoritative, so it responds with answer
- local name server replies to originative node (resolver)
What is a recursive DNS query? - Answers - - when an end node asks a local DNS
server for the IP address for a domain
What is an iterative query? - Answers - - when a name server isn't authoritative for a
domain and must go and find the answer from an authoritative name (by consulting the
root hints file)
What is DNS caching? - Answers - - resolved names are cached by name servers
- subsequent queries use the cached information
True/False: The amount of time information remains cache is not important in DNS
caching. - Answers - False
- must be a limit or else we could never mode servers
The amount of time that a server can hold cached data is determined by the entry's
what? - Answers - - time to live, TTL
Who is responsible for setting the time to live, TTL? - Answers - - zone administrator
