Course 2 – The Bits and Bytes Of Computer Networking

Week 4: Networking Services

Coursera Study Guide


In the fourth week of this course, we’ll explore networking services. We’ll learn about why we need DNS and how it works. We’ll also show you why DHCP makes network administration a simpler task. By the end of this module, you’ll be able to do describe how DNS and DHCP work, how NAT technologies help keep networks secure, and how VPNs and proxies help users connect and stay secured.

Learning Objectives

  • Describe why name resolution is important.
  • Identify the steps involved with a DNS lookup.
  • Understand the most common DNS record types.
  • Explain how DHCP makes network administration a simpler task.
  • Demonstrate how NAT technologies help keep networks secure and preserve IP address space.
  • Describe how VPNs and proxies help users get connected and stay secure.


1. What transport layer protocol does DNS normally use?

  • IP
  • ICMP
  • TCP

Great job! While DNS over TCP does exist, UDP is the most common protocol.

2. A DNS TTL determines what?

  • How long a DNS entry is allowed to be cached (CORRECT)
  • How far away a DNS can be from you
  • How many DNS resolutions can take place before the IP has to change
  • How many steps there are in the resolution process

Awesome! TTL stands for Time to Live and determines how long a DNS entry can be cached.

3. How many root servers are there?

  • 8
  • 13 (CORRECT)
  • 16
  • 17

You got it! There are 13 root servers.


1. An A Record contains what?

  • An IPv4 address (CORRECT)
  • An IPv6 address
  • A fully qualified domain name
  • Yep! An A record contains an IPv4 address.

That’s right! A firewall is used to block certain defined types of traffic.

2. Select all that are true.

  • One domain name can point to one IP. (CORRECT)
  • One domain name can point to many IPs. (CORRECT)
  • Many domain names can point to the same IP. (CORRECT)

That’s right! This is a valid DNS setup.

3. MX stands for ________.

  • Micro extreme
  • Micro exchange
  • Mail exchange (CORRECT)
  • Meta exchange

Correct! An MX record stores a mail server’s IP.

4. A fully qualified domain name can contain how many characters?

  • 63
  • 64
  • 127
  • 255 (CORRECT)

You nailed it! An FQDN is limited to a total length of 255 characters.


1. What are the four things that all computers need configured in order to operate on a modern network? Check all that apply.

  • A TCP port
  • A name server (CORRECT)
  • A MAC address
  • A default gateway (CORRECT)
  • An IP address (CORRECT)
  • An NTP server
  • A subnet mask (CORRECT)

Wohoo! All computers need these four things configured in order to operate on a modern computer network.

2. When using Fixed Allocation DHCP, what’s used to determine a computer’s IP?

  • Location
  • A MAC address (CORRECT)
  • A subnet mask
  • A record

Great job! Fixed Allocation DHCP ensures that computers receive an IP address reserved for it via its MAC address.

3. The process by which a client configured to use DHCP attempts to get network configuration information is known as _________________.

  • DHCP Offer
  • DHCP Acknowledgement
  • DHCP Request
  • DHCP Discovery (CORRECT)

Awesome! DHCP Discovery is how a client determines configuration information.


1. NAT addresses concerns over the dwindling IPv4 address space by ___________________. 

  • allowing networks to use fewer IP addresses overall.
  • allowing users to move to IPv6 when they want.
  • allowing computers using non-routable address space to communicate with the Internet. (CORRECT)
  • performing IP masquerading.

Nice work! NAT allows networks to use non-routable address space for their internal devices.

2. What technique allows for inbound traffic through a NAT?

  • Port preservation
  • Port forwarding (CORRECT)
  • Port authority
  • Ephemeral ports

Right on! Port forwarding is a technique that allows for inbound traffic through a router configured to NAT.

3. The total number of IPv4 addresses is approximately:

  • 4.2 million
  • 4.2 billion (CORRECT)
  • 4.2 trillion
  • Uncountable

Correct! There are approximately 4.2 billion IPv4 addresses. Wowza!


1. Two-factor authentication is_________________________.  

  • a method where you need more than a username and a password. (CORRECT)
  • a method that requires two usernames.
  • a method where you need two passwords.
  • a method where you authenticate twice.

You got it! Two-factor authentication requires a username/password and something extra.

2. VPNs are known as a _____ protocol.

  • tunneling (CORRECT)
  • network layer
  • data link layer
  • connectionless

Nice job! VPNs are tunneling protocols.

3. A proxy is something that _______________________.

  • sends data across a single network segment.
  • allows for many devices to speak to one other device.
  • communicates on behalf of something else. (CORRECT)
  • encrypts traffic sent across the Internet.

Awesome! While proxies are many things, they primarily communicate on behalf of something else.


1. Let’s test your knowledge of networking services! You’re an IT Support Specialist at a new company. As your company grows, your manager asks you to solve various networking problems. Your task is to select the correct network device or server to solve the manager’s request.

Step 1: Read the manager’s request in the top-left corner of the screen. Her request will be highlighted in green.

Step 2: Drag and drop the correct network device or server icon (e.g. DHCP) into the “drop here” area of the screen. If you make a mistake, click the “Reset” or “try again” button and try again.

Step 3: After you have completed all requests, close the quiz window and click the “Submit Quiz” button.

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1. A technique that’s used to route traffic to different destinations, depending on factors like location, congestion, or link health, is known as _____.

  • unicast
  • anycast (CORRECT)
  • multicast
  • broadcast

You got it! Anycast lets you route traffic depending on many factors.

2.  A concept that involves iterating over a list of items one by one in an orderly fashion is known as _______.

  • round robin (CORRECT)
  • recursion
  • authoritative lookup
  • multiplexing

Nice job! Round robin ensures a fairly equal distribution across its members.

3. A _______ record is responsible for resolving an IP to a domain name.

  • NTP
  • TXT

You nailed it! PTR records operate as the inverse of an A Record.

4. NAT stands for ______.

  • National Academic Translation
  • Networking Association Team
  • Network Address Translation (CORRECT)
  • Network Acknowledgement Track

Well done! NAT, or Network Address Translation, allows for a device to rewrite the source IP in a packet.

5. When NAT hides the source IP of an originating device, this is known as ________.

  • port forwarding
  • routing
  • switching
  • IP masquerading (CORRECT)

Correct! IP masquerading means that the destination will never know the actual IP of the source.

6. A company moves a popular website to a new web host. Which of the following will change as a result?

  • Internet Protocol (IP) address (CORRECT)
  • Network service
  • Root name server
  • Domain name

Woohoo! The IP address will certainly change. However, with DNS in place the name stays the same and users will never know that the website moved.

7. The “www” portion of a domain is known by which of the given options? Check all that apply.

  • Subdomain (CORRECT)
  • Fully Qualified Domain Name (FQDN)
  • Top Level Domain (TLD) name
  • Host name (CORRECT)

You nailed it! A subdomain like “www” precedes the domain name and is used to further identify a system and its purpose.

Great work! A host name is used to identify a machine and its purpose. “www” and “host1” are examples of host names.

8. Which of the following allows computers on a network to automatically receive address assignment information?

  • Primary gateway
  • Dynamic Host Protocol (DHCP) (CORRECT)
  • Domain Name System (DNS)
  • Time to Live (TTL)

Right on! DHCP is used to automatically assign IP addresses to devices on a network.

9. Which technique is used with Network Address Translation (NAT) where a source port chosen by a client is the same port used by a router?

  • Preservation (CORRECT)
  • Forwarding
  • Masquerading
  • Translation

Well done! Preservation helps a router determine which traffic belongs to which host when using NAT.

10. What technology helps users get connected and stay secure?

  • Virtual Private Network (VPN) (CORRECT)
  • Domain Name System (DNS)
  • Dynamic Host Configuration Protocol (DHCP)
  • Network Address Translation (NAT)

Awesome! A VPN is used by clients to connect securely to a private network.

11. What port on a name server is used for User Datagram Protocol (UDP) name request packets?

  • 22
  • 53 (CORRECT)
  • 25
  • 80

Woohoo! DNS uses port 53 over UDP for name resolution communications.

12. A new Domain Name System (DNS) server is being configured. Which record type is used to declare a new zone?

  • Mail Exchanger (MX)
  • Pointer (PTR)
  • Name server (NS)
  • Start of Authority (SOA) (CORRECT)

Great work! An SOA record establishes a zone and maintains authority over the zone.

13. Which of the following is NOT configured by a Dynamic Host Protocol (DHCP) server?

  • Subnet mask address
  • Internet Protocol (IP) address
  • Media Access Control (MAC) address (CORRECT)
  • Gateway address

You got it! A MAC address is a hardware address assigned to a device by the manufacturer.

14. IANA has primarily been responsible with assigning address blocks to five regional internet registries (RIR). A tech needs to research address blocks assigned in the United States. Which RIR should the tech contact?

  • RIPE

Woohoo! ARIN primarily serves the United States and Canada.

15. What service acts on behalf of a client in order to access another service?

  • Virtual Private Network (VPN) Tunnel
  • Proxy Server (CORRECT)
  • Domain Name System (DNS)
  • Dynamic Host Configuration Protocol (DHCP)

Nice job! Proxies sit between clients and other servers to facilitate connections.

16. When a client computer sends a request to a Domain Name System (DNS) server, what type of packet is sent?

  • ACK
  • TCP

Awesome! The requesting client initiates a query with a DNS server by sending a Synchronize (SYN) packet as a first step in the three-way handshake.

17. Administration and definition of TLDs are handled by a non-profit organization known as _______.

  • FQDN
  • DHCP

Wohoo! ICANN is responsible for maintaining the global domain name system.

18. VPN stands for _______

  • Very Personal Network
  • Virtual Private Network (CORRECT)
  • Virtual Public Network
  • Virtual Proxy Network

You got it! A VPN allows a device to establish an encrypted tunnel to another network.

19. A video conferencing application isn’t working due to a Domain Name System (DNS) port error. Which record requires modification to fix the issue?

  • Canonical name (CNAME)
  • Host (A)
  • Text (TXT)
  • Service record (SRV) (CORRECT)

Great work! A service record is used to set parameters, like the protocol and ports used for a service with a domain name.

20. Network Address Translation (NAT) is typically implemented with which hardware devices? Check all that apply.

  • Firewalls (CORRECT)
  • Hubs
  • Routers (CORRECT)
  • Switches

Great work! A firewall provides network protection. Most firewalls can provide NAT services.

You got it! A router is used on a network for a number of reasons, including NAT.

21. A complete Fully Qualified Domain Name (FQDN) is limited to how many characters?

  • 63
  • 255 (CORRECT)
  • 53
  • 127

Awesome! A complete FQDN can be up to 255 characters.

22. During the name resolution process, which technique is used to avoid congestion when querying a server?

  • Redirect
  • Hierarchy
  • Lookup
  • Anycast (CORRECT)

You got it! Anycast allows a request to be sent to an appropriate server based on factors, like location. This helps relieve severe congestion.

23. DNS stands for _________.

  • Do Not Signal
  • Domain Name System (CORRECT)
  • Dynamic Name Server
  • Diversified Nomenclature System

Yep! DNS stands for Domain Name System.

24. Which type of Domain Name System (DNS) server performs a full name resolution request?

  • Authoritative name server
  • Root name server
  • Caching name server
  • Recursive name server (CORRECT)

Right on! A recursive name server performs a full DNS resolution request.

25. Network Address Translation (NAT) technology provides a major benefit for which of these network problems?

  • Address exhaustion (CORRECT)
  • Port Preservation
  • Routable addresses
  • Assigning Internet Protocol (IP) address blocks

You got it! NAT helps to remedy the concern of IP address shortages by mapping private to public addresses.

26. What benefits does the Domain Name System (DNS) provide? Check all that apply.

  • Assigning Internet Protocol (IP) addresses
  • Easy mapping to a new Internet Protocol (IP) address (CORRECT)
  • Network Address Translation (NAT)
  • Ease of address memorization (CORRECT)

Great work! DNS easily maps to a system’s IP address, even if that address changes.

Woohoo! With DNS in place, there is no need to memorize hard to remember IP addresses.

27. What term defines keeping the address of one computer secret from another?

  • Rewriting
  • Masquerading (CORRECT)
  • Translation
  • Preservation

Right on! Masquerading is when NAT is used to hide the IP of a computer from another.

28. The Domain Name System (DNS) provides an easy way to remember addresses. Without DNS, how many octets for an Internet Protocol (IP) address would have to be memorized?

  • 4 (CORRECT)
  • 48
  • 32
  • 10101010

Great work! An IP address is presented with 4 octets separated by decimals, like