Modules 9 – 12: Data Communications and Network Services Pre-Test Exam Answers

Networking Essentials ( Version 2) – Modules 9 – 12: Data Communications and Network Services Pre-Test Exam

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1. Which two reasons generally make DHCP the preferred method of assigning IP addresses to hosts on large networks? (Choose two.)

  • It provides an address only to devices that are authorized to be connected to the network.
  • It ensures that addresses are only applied to devices that require a permanent address.
  • It eliminates most address configuration errors.
  • It reduces the burden on network support staff.
  • It guarantees that every device that needs an address will get one.

Explanation: DHCP is generally the preferred method of assigning IP addresses to hosts on large networks because it reduces the burden on network support staff and virtually eliminates entry errors. However, DHCP itself does not discriminate between authorized and unauthorized devices and will assign configuration parameters to all requesting devices. DHCP servers are usually configured to assign addresses from a subnet range, so there is no guarantee that every device that needs an address will get one.

2. Which two types of devices are typically assigned static IP addresses? (Choose two.)

  • hubs
  • printers
  • laptops
  • web servers
  • workstations

Explanation: Servers and peripherals are often accessed by an IP address, so these devices need predictable IP addresses. End-user devices often have dynamic addresses that are assigned. Hubs do not require IPv4 addresses to operate as intermediary devices.

3. If more than one DHCP server is available on the local network, in which order will DHCP messages be sent between a host and a DHCP server?

  • request, discover, offer, acknowledgment
  • discover, offer, request, acknowledgment
  • request, acknowledgment, discover, offer
  • acknowledgment, request, offer, discover

Explanation: A DHCP host broadcasts a DHCP discover message to locate available servers. If more than one DHCP server is available, each server will respond to the host with a unicast DHCP offer message, which offers a lease to the client. The client then broadcasts a DHCP request message that identifies the specific server and offer that the client will accept. The identified server will unicast a DHCP acknowledgment message to finalize the offer.

4. Which destination IPv4 address does a DHCPv4 client use to send the initial DHCP Discover packet when the client is looking for a DHCP server?

  • the IP address of the default gateway
  • 255.255.255.255
  • 127.0.0.1
  • 224.0.0.1

Explanation: Broadcast communications on a network may be directed or limited. A directed broadcast is sent to all hosts on a specific network. A limited broadcast is sent to 255.255.255.255. When a DHCP client needs to send a DHCP Discover packet in order to seek DHCP servers, the client will use this IP address of 255.255.255.255 as the destination in the IP header because it has no knowledge of the IP addresses of DHCP servers.

5. Which characteristic describes the default gateway of a host computer?

  • the logical address of the router interface on the same network as the host computer
  • the logical address assigned to the switch interface connected to the router
  • the physical address of the router interface on the same network as the host computer
  • the physical address of the switch interface connected to the host computer

Explanation: The default gateway is the IP address of an interface on the router on the same network as the sending host.

6. Typically, which network device would be used to perform NAT for a corporate environment?

  • host device
  • switch
  • server
  • router
  • DHCP server

Explanation: Typically, the translation from private IP addresses to public IP addresses is performed on routers in corporate environments. In a home environment, this device might be an access point that has routing capability or the DSL or cable router.

7. Which network technology allows devices to communicate using both IPv4 and IPv6 addressing at the same time?

  • tunneling
  • NAT64
  • dual stack
  • SLAAC

Explanation: Dual stack allows IPv4 and IPv6 protocol stacks to function on devices at the same time. This allows devices to communicate on a network that uses both IPv4 addressing and IPv6 addressing simultaneously.

8. What is the IPv6 prefix that is used for link-local addresses?

  • FF01::/8
  • FC00::/7
  • FE80::/10
  • 2001::/3

Explanation: The IPv6 link-local prefix is FE80::/10 and is used to create a link-local IPv6 address on an interface.

9. What type of applications are best suited for using UDP?

  • applications that are sensitive to delay
  • applications that need reliable delivery
  • applications that require retransmission of lost segments
  • applications that are sensitive to packet loss

Explanation: UDP is not a connection-oriented protocol and does not provide retransmission, sequencing, or flow control mechanisms. It provides basic transport layer functions with a much lower overhead than TCP. Lower overhead makes UDP suitable for applications which are sensitive to delay.

10. A destination PC receives an email message with the sequence numbers on packets out of order. Which layer of the TCP/IP model is responsible for reassembling the packets of the message in the correct order?

  • network access
  • internet
  • application
  • transport

Explanation: The transport layer of the TCP/IP model is responsible for ensuring that all packets in a message are received, reassembling the message in the correct order after all packets are received, and identifying which applications are sending and receiving network data.

11. Which action is performed by a client when establishing communication with a server via the use of UDP at the transport layer?

  • The client sends a synchronization segment to begin the session.
  • The client randomly selects a source port number.
  • The client sets the window size for the session.
  • The client sends an ISN to the server to start the 3-way handshake.

Explanation: Because a session does not have to be established for UDP, the client selects a random source port to begin a connection. The random port number selected is inserted into the source port field of the UDP header.

12. A client device has initiated a secure HTTP request to a web browser. Which well-known port address number is associated with the destination address?

  • 443
  • 110
  • 404
  • 80

Explanation: Port numbers are used in TCP and UDP communications to differentiate between the various services running on a device. The well-known port number used by HTTPs is port 443.

13. Refer to the exhibit. Which protocol allows a user to type www.cisco.com instead of an IP address to access the web server?
Modules 9 - 12: Data Communications and Network Services Pre-Test Exam Answers 1

  • FTP
  • DNS
  • HTML
  • SNMP
  • HTTP

Explanation: Web servers are assigned static IP addresses. They are also registered with domain names so people can remember them easily. However, web servers are connected through their IP addresses. DNS provides the service to map the domain name to its IP address.

14. Which protocol is used to transfer web pages from a server to a client device?

  • SMTP
  • SSH
  • POP
  • HTML
  • HTTP

Explanation: The Hypertext Transfer Protocol (HTTP) provides services between a web browser requesting web pages and a web server responding to the requests. HTML (Hypertext Markup Language) is a markup language to instruct a web browser how to interpret and display a web page.

15. What two characteristics describe an FTP connection? (Choose two.)

  • A large file requires more than two connections between the client and the server to successfully download it.
  • The server establishes the first connection with the client to control traffic that consists of server commands and client replies.
  • Files can be downloaded from or uploaded to the server.
  • The first connection established is for traffic control and the second connection is created to transfer a file.
  • The client needs to run a daemon program to establish an FTP connection with a server.

Explanation: An FTP client is an application that runs on a computer used to push and pull files from a server running an FTP daemon. To transfer files, FTP requires two connections between the client and the server: one for commands and replies and another for the actual file transfer. The client establishes the first connection to the server for control traffic and the second connection for the actual file transfer. This connection is created every time there is a file to be transferred. The client can download a file from or upload a file to the server.

16. Which protocol retains a message in a mailbox on a server, even after the message is accessed by a user on a local client device?

  • IMAP4
  • SMTP
  • DNS
  • POP3

Explanation: The IMAP4 protocol will keep any message accessed by a client device in the mailbox on the server. The message is removed from the mailbox only after it is deleted by a user on the client device.


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