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

Module Group 3: Modules 9 – 12 Group Exam Answers

Networking Essentials (Version 2) – Modules 9 – 12: Data Communications and Network Services Group Exam Answers

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1. A DHCP server is used to assign IP addresses dynamically to the hosts on a network. The address pool is configured with 172.30.8.0/24. There are 7 printers on this network that need to use reserved static IP addresses from the pool. How many IP addresses in the pool are left to be assigned to other hosts?

• 254
• 249
• 251
• 247

Explanation: If the block of addresses allocated to the pool is 172.30.8.0/24, there are 254 IP addresses to be assigned to hosts on the network. As there are 7 printers which need to have their addresses assigned statically, then there are 247 IP addresses left for assignment.

2. An employee is having connectivity issues. Why might a network technician try to ping the default gateway from the employee laptop?

• to determine if the laptop address is included in the DNS server
• to verify that an IP address was provided by the DHCP server
• to verify connectivity with the device that provides access to remote networks
• to verify that the SVI interface on the switch is configured correctly

Explanation: The default gateway address is usually the address of the router interface. The router provides access to remote networks, so a successful ping to the default gateway would mean that the laptop is able to communicate with the router.

3. How many bits make up the single IPv6 hextet :10CD:?

• 32
• 8
• 4
• 16

Explanation: A hextet consists of 4 hexadecimal characters. Each hexadecimal character is represented by four bits, giving a total of 16 bits.

4. Which three pieces of information are identified by a URL? (Choose three.)

• the protocol that is being used
• the version of the browser
• the location of the resource
• the domain name that is being accessed
• the IP address of the gateway
• the MAC address of the web server

Explanation: URLs are used to access specific content on a web server through a web browser. The URL identifies the protocol that is being used such as HTTP or FTP, the domain of the server, and the location of the resource on the server.

5. Which type of applications are best suited to use UDP as the transport layer protocol?

• applications that require flow control
• applications that require stateful sessions
• applications that require minimal transmission delay
• applications that require data to be reassembled in a specific order

Explanation: UDP is a light-weight connectionless protocol that is well-suited for applications that are susceptible to delay or that do not need the features provided by TCP (guaranteed delivery, flow control, or sequencing).

6. Open the PT Activity. Perform the tasks in the activity instructions and then answer the question. What is the IP address of this server?

• 209.165.201.4
• 192.168.10.1
• 209.165.201.3
• 192.168.10.100

Explanation: The DNS server resolves Internet names to associated IP addresses.

7. What type of server would use IMAP?

• email
• DHCP
• FTP
• Telnet
• DNS

Explanation: SMTP, IMAP, and POP are three application layer protocols for email applications.

8. Which three types of nodes should be assigned static IP addresses on a network? (Choose three.)

• mobile laptops
• tablets
• desktop PCs
• gateways
• servers
• printers

Explanation: Servers, printers, and intermediary devices, such as routers, switches, and access points should have statically assigned IP addresses so that they are accessible to users and available for remote management.

9. Why is DHCP for IPv4 preferred for use on large networks?

• Large networks send more requests for domain to IP address resolution than do smaller networks.
• DHCP uses a reliable transport layer protocol.
• It prevents sharing of files that are copyrighted.
• It is a more efficient way to manage IPv4 addresses than static address assignment is.
• Hosts on large networks require more IPv4 addressing configuration settings than do hosts on small networks.

Explanation: Static IPv4 address assignment requires personnel to configure each network host with addresses manually. Large networks can change frequently and have many more hosts to configure than do small networks. DHCP provides a much more efficient means of configuring and managing IPv4 addresses on large networks than does static address assignment.

10. Refer to the exhibit. PC1 is configured to obtain a dynamic IP address from the DHCP server. PC1 has been shut down for two weeks. When PC1 boots and tries to request an available IP address, which destination IP address will PC1 place in the IP header?

• 255.255.255.255
• 192.168.1.1
• 192.168.1.8
• 192.168.1.255

Explanation: When a host boots and has been configured for dynamic IP addressing, the device tries to obtain a valid IP address. It sends a DHCPDISCOVER message. This is a broadcast message because the DHCP server address is unknown (by design). The destination IP address in the IP header is 255.255.255.255 and the destination MAC address is FF:FF:FF:FF:FF:FF.

11. Which message does an IPv4 host use to reply when it receives a DHCPOFFER message from a DHCP server?

• DHCPACK
• DHCPREQUEST
• DHCPOFFER
• DHCPDISCOVER

Explanation: When the client receives the DHCPOFFER from the server, it sends back a DHCPREQUEST broadcast message. On receiving the DHCPREQUEST message, the server replies with a unicast DHCPACK message.

12. A host PC is attempting to lease an address through DHCP. What message is sent by the server to let the client know it is able to use the provided IP information?

• DHCPDISCOVER
• DHCPOFFER
• DHCPREQUEST
• DHCPACK
• DHCPNACK

Explanation: When a host uses DHCP to automatically configure an IP address, the typically sends two messages: the DHCPDISCOVER message and the DHCPREQUEST message. These two messages are usually sent as broadcasts to ensure that all DHCP servers receive them. The servers respond to these messages using DHCPOFFER, DHCPACK, and DHCPNACK messages, depending on the circumstance.

13. How is a DHCPDISCOVER transmitted on a network to reach a DHCP server?

• A DHCPDISCOVER message is sent with the broadcast IP address as the destination address.
• A DHCPDISCOVER message is sent with the IP address of the default gateway as the destination address.
• A DHCPDISCOVER message is sent with a multicast IP address that all DHCP servers listen to as the destination address.
• A DHCPDISCOVER message is sent with the IP address of the DHCP server as the destination address.

Explanation: The DHCPDISCOVER message is sent by a DHCPv4 client and targets a broadcast IP along with the destination port 67. The DHCPv4 server or servers respond to the DHCPv4 clients by targeting port 68.

14. What is the result if the default gateway address is misconfigured on a PC?

• The PC can communicate with devices in remote networks but not with those in the same network.
• The PC can communicate with devices in the same network but not with those in remote networks.
• The PC cannot communicate with any devices.
• The PC can communicate with devices both in remote networks and in the same network.

Explanation: The default gateway for a PC is the closest networking device that can forward traffic to other networks. If a PC has an incorrect or nonexistent default gateway address, it will not be able to communicate with devices in remote networks. However, communication would occur between devices in the same network with or without a default gateway.

15. Which statement accurately describes dynamic NAT?

• It provides a mapping of internal host names to IP addresses.
• It provides an automated mapping of inside local to inside global IP addresses.
• It dynamically provides IP addressing to internal hosts.
• It always maps a private IP address to a public IP address.

Explanation: Dynamic NAT provides a dynamic mapping of inside local to inside global IP addresses. NAT is merely the one-to-one mapping of one address to another address without taking into account whether the address is public or private. DHCP is automatic assignment of IP addresses to hosts. DNS is mapping host names to IP addresses.

16. What purpose does NAT64 serve in IPv6?

• It converts regular IPv6 addresses into 64-bit addresses that can be used on the Internet.
• It converts the 48-bit MAC address into a 64-bit host address that can be used for automatic host addressing.
• It enables companies to use IPv6 unique local addresses in the network.
• It translates private IPv6 addresses into public IPv6 addresses.
• It converts IPv6 packets into IPv4 packets.

Explanation: NAT64 is typically used in IPv6 when networks are being transitioned from IPv4 to IPv6. It allows the IPv6 networks to connect to IPv4 networks (such as the Internet), and works by translating the IPv6 packets into IPv4 packets.

17. Which type of IPv6 address is not routable and used only for communication on a single subnet?

• unique local address
• unspecified address
• loopback address
• global unicast address
• link-local address

Explanation: Link-local addresses have relevance only on the local link. Routers will not forward packets that include a link-local address as either the source or destination address.

18. What is the valid most compressed format possible of the IPv6 address 2001:0DB8:0000:AB00:0000:0000:0000:1234?

• 2001:DB8:0:AB:0:1234
• 2001:DB8:0:AB00::1234
• 2001:DB8:0:AB::1234
• 2001:DB8::AB00::1234

Explanation: There are two rules defining how an IPv6 address can be compressed. The first rule states that leading zeros in a hextet can be eliminated. The second rule states that a single :: can be used to represent one or more contiguous all zero hextets. There can be one and only one :: in an IPv6 address.

19. What is an advantage of UDP over TCP?

• UDP communication is more reliable.
• UDP communication requires less overhead.
• UDP acknowledges received data.
• UDP reorders segments that are received out of order.

Explanation: TCP is a more reliable protocol and uses sequence numbers to realign packets that arrive out of order at the destination. Both UDP and TCP use port numbers to identify applications. UDP has less overhead than TCP because the UDP header has fewer bytes and UDP does not confirm the receipt of packets.

20. What layer of the TCP/IP suite makes sure that all the data packets of a message arrive safely at the destination?

• transport
• application
• network access
• internet

Explanation: The transport layer is responsible for managing the delivery of packets. TCP monitors the packets and if a packet is missing, it will request that it be sent again.

21. How does a client computer determine what source port number to assign to a UDP header?

• The port number is random within the range of dynamic port numbers.
• The port number is based on a well-known port number that is open on the destination device.
• The port number is based on the application that created the data.
• The port number is based on a well-known port number that is assigned to the application on the sending device.

Explanation: The destination port number is normally a well-known or registered port number that is open on the destination device such as a server. The source port is randomly generated by the client computer from the 49152 to 65535 range.

22. What is a socket?

• the combination of a source IP address and port number or a destination IP address and port number
• the combination of the source and destination IP address and source and destination Ethernet address
• the combination of the source and destination sequence and acknowledgment numbers
• the combination of the source and destination sequence numbers and port numbers

Explanation: A socket is a combination of the source IP address and source port or the destination IP address and the destination port number.

23. What is the purpose of using a source port number in a TCP communication?

• to assemble the segments that arrived out of order
• to inquire for a nonreceived segment
• to keep track of multiple conversations between devices
• to notify the remote device that the conversation is over

Explanation: The source port number in a segment header is used to keep track of multiple conversations between devices. It is also used to keep an open entry for the response from the server. The incorrect options are more related to flow control and guaranteed delivery.

24. Which two protocols are used in the process of sending and receiving emails? (Choose two.)

• HTTP
• SSH
• FTP
• POP
• SMTP

Explanation: POP and SMTP are protocols used for email. POP is Post Office Protocol and is used by clients to retrieve email messages from a server. SMTP is Simple Mail Transfer Protocol and is used by clients to send email messages to a server.​

25. What is a function of a DNS server?

• It maps IP addresses to physical addresses.
• It assigns logical address information to host computers.
• It determines the IP address that is associated with a specific host domain name.
• It translates private IP addresses to public IP addresses.

Explanation: Hosts are assigned with IP addresses in order to communicate over the network. Hosts are registered with domain names so people can remember and recognize them easily. However, computers are connected through their IP addresses. DNS provides the service to map the domain name to its IP address.

26. Match the term to a function.

• web server: hosts a web page
• web client: requests a web page
• HTML: used to create web pages
• HTTPS: secure protocol that uses port 443
• HTTP: protocol commonly used by a web browser

27. Open the PT Activity. Perform the tasks in the activity instructions and then answer the question. What message is displayed on the webpage?

• A web server provides secure communication!
• A web server should run secure services!
• A secure web server is the way to go!
• A secure web server is running!

Explanation: Because the HQ web server runs a secure web service, the protocol HTTPS must be used to access the website. This means that the URL of https://www.cisco.com must be used to access the HQ web server and locate the message.

28. Which two applications provide virtual terminal access to remote servers? (Choose two.)

• DHCP
• SMTP
• SSH
• DNS
• Telnet

Explanation: Telnet and SSH are two services that provide virtual terminal services to servers. DNS maps a domain name to its IP address. DHCP provides dynamic IP addressing information. SMTP provides email service.