M3Q15: Domain Name System

Question 1

Which DNS record needs to be setup to point the outside world to a company’s E-Mail server?

A. An A Record
B. NS Record
C. CNAME
D. MX Record

Answer 1

D. MX Record

Explanation: MX records are Mail Exchanger records which are used for Mail servers.

Question 2

A user is having problems accessing websites. You step in to troubleshoot and you are able to send pings to the default gateway and out to public internet IP addresses just fine.

However, when you try to ping to a Fully Qualified Domain Name (FQDN) such as www.google.com it does not go through and says “could not find host www.google.com”.

Also, when you attempt to browse to a website using a web browser you get an error stating the site can’t be reach and the
DNS address could not be found. What is most likely the cause of this problem?

A. The DNS Server is down
B. The user has an incorrect IP address in TCP/IP settings
C. The user has an incorrect DNS server address in TCP/IP settings
D. DHCP Server is down

Answer 2

C. The user has an incorrect DNS server address in TCP/IP settings

Explanation: When an bad DNS entry has been input into the TCP/IP settings of a computer it will not be able to perform DNS lookups. It will seem to the user as if the connection to the internet is down, but in reality the computer just can’t perform DNS lookups. To correct this a valid DNS server should be input into the TCP/IP settings of the computer.

Question 3

The Domain Name System provides translation from Fully Qualified Domain Names (FQDNs) into IP addresses.

A. True
B. False

Answer 3

A. True

Explanation: The purpose of DNS is to make things like web services and server addresses much easier to manage. It’s not easy to remember IP addresses (even for techs and engineers) and also, what if we need the IP addresses to change? Then, everyone would need to remember a new number! DNS allows us to use names instead of IP addresses and assists with making management of public and even private servers much easier. With DNS we can always keep the same names for our websites and servers and simply translate those names into whatever IP addresses we need to. DNS resolves FQDNs into IP addresses and vice versa.

Question 4

A FQDN (Fully Qualified Domain Name) contains the following levels.
*(choose all that apply)*

A. Root Domain
B. Top-level Domain
C. Second-level Domain
D. Host

Answer 4

ALL - A. (Root Domain), B. (Top-level Domain), C. (Second-level Domain), D. (Host)

• *Explanation:** FQDNs are made up of all of the above. For example in the FQDN
  www. google.com, www is the Host, .google is the Second-level, .com is the Top-leve, and the Root Domain is an invisible “.” at the end of the FQDN.

Question 5

This type of service allows one to use a dynamically assigned public IP address with a public DNS record.

A. SOA
B. DHCP
C. SRV
D. DDNS

Answer 5

D. DDNS

Explanation: DDNS (Dynamic DNS) is a service that allows you to publish a public DNS record even if you have a dynamically assigned public IP address from your service provider. Most companies use static IP addresses on their internet gateways and use their own DNS, so in those situations DDNS is not necessary. However, for home users or SOHO companies that don’t have a static IP address DDNS is a good option for setting a standard public DNS name that doesn’t change and will always translate to your public IP address even when it changes.