DNS Facts

Question 1

DNS

Answer 1

domain name system

Question 2

FQDN

Answer 2

fully qualified domain name is a domain name that spells out each level of the hierarchy. For example, www.testout.com. is a FQDN. The following table describes each section of the FQDN.

Question 3

Root Level

Answer 3

The highest level in the DNS hierarchy. The DNS root level is represented by a period at the end of the of the FQDN.

When typing the FQDN into a web browser, the period is typically not included. The period is mainly used when defining DNS records on the server.

Question 4

Top-level domain (TLD)

Answer 4

The next highest level in the DNS hierarchy. TLDs have extensions such as com, edu, gov, org, etc.

Question 5

Domain name

Answer 5

The name unique to each organization. The DNS domain is referred to as distributed because this portion is unique to each organization or group.

Each organization is responsible for maintaining its own namespace.

Question 6

Hostname

Answer 6

This is the name of specific hosts on the network.
On an internal network, an example of a hostname could be server1 or server2.
On the internet, this is typically www.
On a webserver, www may be the name of the root folder that all website files are stored in.

Question 7

DNS Process

Answer 7

When a web browser sends a DNS request to discover the IP address of the requested site, the name resolution process that occurs involves multiple servers. The following table describes each of these servers:

Question 8

Root server

Answer 8

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

While there are only 13 root servers, there are multiple copies of these servers spread out across the globe that are mapped to the same IP addresses to handle all DNSrequests.

Question 9

Top-level domain (TLD) server

Answer 9

The TLD servers contain the information for all websites that share a common domain extension, such as .com or .org.

Question 10

Authoritative name server

Answer 10

This is the server that contains the DNS information for a site or domain such as testout.com. The server is authoritative because it doesn’t have to ask any other DNS server for help; it holds the information already.

There are usually two authoritative DNS servers per domain.

Question 11

Recursive server

Answer 11

The recursive server handles the DNS name resolution process.

Question 12

HOSTS file

Answer 12

The HOSTS file is a local text file on each computer that maps hostnames to IP addresses. The HOSTS file was used previously for smaller networks but is too complicated to use on networks or the internet.

Even though the HOSTS file is rarely used today, it is still the first place that a computer looks during the name resolution process.

Question 13

A (host address)

Answer 13

Maps an IPv4 (32-bit) DNS host name to an IP address. This is the most common resource record type.

Question 14

AAAA (quad-A)

Answer 14

Maps an IPv6 (128-bit) DNS host name to an IP address.

Question 15

Pointer (PTR)

Answer 15

Maps an IP address to a host name (by pointing to an A record).

Question 16

Canonical name (CNAME)

Answer 16

Provides alternate names (or aliases) to hosts that already have a host record. For example:
sales.testout can be mapped to the IP address of testout.com
If a single A record is used with multiple CNAME records, only the A record needs to be modified when the IP address changes.

Question 17

Mail exchange (MX)

Answer 17

Identifies servers used for handling email.

Question 18

TXT

Answer 18

Stores plaintext notes in a DNS zone. This record type can be used to help verify domain ownership and prevent email spam.

Question 19

Start of Authority (SOA)

Answer 19

Stores all the administration information about the DNS zone. For example, the administrator’s email address, TTL values, primary name server, and more information is recorded in this file.

SOA records are very important in the zone transfer process.

Question 20

Name server (NS)

Answer 20

Defines the authoritative server for a specific domain. This record identifies all name servers that can perform name resolution for the zone.

Typically, there is an entry for the primary server and all secondary servers for the zone (all authoritative DNS servers).

Question 21

DNS service (SRV)

Answer 21

Defines a host and port for a specific service, such as voice over IP. This allows clients to find services through DNS. Windows automatically creates these records as needed.