chapter3

Question 1

dns stands for

Answer 1

domain name system

Question 2

why do we need dns

Answer 2

When we type in http://www.msn.com/home.aspx, the browser needs to look up the IP address of the web servers name (host name) www.msn.com

If we do a ping to www.google.com we first need to convert the hostname to an ip address

Question 3

alternative to dns + explanation

Answer 3

WINS
store netbios computer names (max 5 char) in a non hierarchical database

Question 4

how can we do name resolution + requirements for this

Answer 4

DNS servers in your own network, or via the internet

WINS servers (for windows 2000)

Broadcast (as last option and least efficient way)

Requirements -> web servers or servers in your own network must be registrered with the DNS server (auto or manually)

Question 5

give an overview of DNS

Answer 5

DNS is a hierarchical distributed system

Dns is the foundation of the internet naming scheme

Dns supports accessing resources by using alphanumeric names

interNIC is responsible for managing the domain namespace

dns was created to support the internet’s growing number of hosts

Question 6

rules of dns naming and fqdn names

Answer 6

a through z

A through Z

0 through 9

Hyphen (-)

Underscore (_) is a reserved character

Question 7

what is a FQDN or fully qualified domain name

Answer 7

behind these names is one or more IP address in the DNS database

Question 8

components in a dns query + explanation

Answer 8

Dns client = dns client is a device that has a host name query, this can be a server or a client Pc or any device

Dns server = dns server is a device that has a dns service (linux, unix, windows based) and this device maintains a database of hostnames, this database is called a zone file

Dns servers on the internet

Question 9

what is a dns query

Answer 9

Queries are recursive or iterative

Dns clients and dns servers both initiate queries

Dns servers are authoritative or non authoritative for a namespace
Authoritative dns server for the namespace will either:
Return the requested IP address
Return an authoritative “No”

Nonauthoritative dns server for the namespace will either:
Check its chache
Use forwarders
Use root hints

A query is a request for name resolution and is directed to a dns server

Question 10

what is a recursive query

Answer 10

A recursive query is sent to dns server and requires a complete answer

Question 11

what is a iterative query

Answer 11

A iterative query is sent to a dns server and may be answered with a referral to another dns server

Question 12

what is a forwarder and explain

Answer 12

A forwarder is a dns server designated to resolve external or offsite dns domain names, advantage is that the answer is stored in the forwarder’s chache. Every other dns server that uses the forwarder will be able to use this cache to get an answer faster

Question 13

what is conditional forwarding

Answer 13

Conditional forwarding forwards requests using a domain name condition

Question 14

what are root hints

Answer 14

Root hints contain the IP addresses for dns root servers

Question 15

explain cache

Answer 15

Everything that is chached in the cache will remain for a certain ttl or time to live, after that it automatically disappears from the cache. When restarting the dns client or server device this cache will also be cleared

Question 16

give record types + explanation

Answer 16

A = resolves a host name to an IP address

PTR = resolves an IP address to a host name

SOA = the first record in any zone file

SRV = resolves names of servers providing services

NS = indentifies the dns server for each zone

MX = the mail server

CNAME = resolves an alias to a host name

Question 17

give dns zone types + explanation

Answer 17

Primary = read/write copy of a dns database, can be updated auto or manually

Secondary = read only copy of an dns database, cannot be updated

Stub = copy of a zone that contains only records used to locate name servers

Active directory integrated = zone data is stored in active directory rather than in zone files

Question 18

give the types of lookup zones + explanation

Answer 18

Forward lookup zone = forward lookup zone is a primary zone that contains host names and can resolve them to ip addresses

reverse lookup zone = reverse lookup zone is a primary zone that contains ip addresses and returns host names linked to them