Module 7: Connectivity Verification Quiz Answers

1. What is indicated by a successful ping to the ::1 IPv6 address?

  • All hosts on the local link are available.
  • The link-local address is correctly configured.
  • The default gateway address is correctly configured.
  • IP is properly installed on the host.
  • The host is cabled properly.

Explanation: The IPv6 address ::1 is the loopback address. A successful ping to this address means that the TCP/IP stack is correctly installed. It does not mean that any addresses are correctly configured.

2. A user complains that the workstation cannot access the network. The network technician asks the user to issue the ping 127.0.0.1 command. What is the purpose of using this command?

  • to test the reachability of a remote network
  • to check that the workstation can reach a DHCP server
  • to verify that the TCP/IP stack is operational
  • to verify that the NIC is configured with a static address

Explanation: The ping 127.0.0.1 command is used to verify the proper operation of the TCP/IP protocol stack from the network layer to the physical layer – and back. This operation of this command does not actually put a signal on the network media.

3. What process is used in ICMPv6 for a host to verify that an IPv6 address is unique before configuring it on an interface?

  • SLAAC
  • EUI-64
  • DAD
  • ARP

Explanation: Before an IPv6 host can enable and use an assigned IPv6 address, the host must verify that the address is unique on the network. To verify that no other hosts are using the IPv6 address, the host performs the duplicate address detection (DAD) process by sending a Neighbor Solicitation (NS) message to the IPv6 address.

4. A network administrator can successfully ping the server at www.cisco.com, but cannot ping the company web server located at an ISP in another city. Which tool or command would help identify the specific router where the packet was lost or delayed?

  • telnet
  • netstat
  • ipconfig
  • traceroute

Explanation: The traceroute command provides connectivity information about the path a packet takes to reach the destination and about every router (hop) along the way. It also indicates how long a packet takes to get from the source to each hop and back.

5. A user executes a traceroute over IPv6. At what point would a router in the path to the destination device drop the packet?

  • when the value of the Hop Limit field reaches 255
  • when the target host responds with an ICMP echo reply message
  • when the value of the Hop Limit field reaches zero
  • when the router receives an ICMP time exceeded message

Explanation: When a traceroute is performed, the value in the Hop Limit field of an IPv6 packet determines how many router hops the packet can travel. Once the Hop Limit field reaches a value of zero, it can no longer be forwarded and the receiving router will drop the packet.

6. Which ICMPv6 message is sent when the IPv6 hop limit field of a packet is decremented to zero and the packet cannot be forwarded?

  • network unreachable
  • port unreachable
  • protocol unreachable
  • time exceeded

Explanation: ICMPv6 uses the hop limit field in the IPv6 packet header to determine if the packet has expired. If the hop limit field has reached zero, a router will send a time exceeded message back towards the source indicating that the router cannot forward the packet.

7. What message is sent by a host to check the uniqueness of an IPv6 address before using that address?

  • ARP request
  • echo request
  • router solicitation
  • neighbor solicitation

Explanation: In IPv6, Duplicate Address Detection (DAD) is used in place of ARP. An IPv6 host performs DAD by sending a neighbor solicitation (NS) message to its own IPv6 address to ensure the uniqueness of the address prior to using it.

8. Which protocol is used by ping to test connectivity between network hosts?

  • ARP
  • DHCP
  • ICMP
  • TCP

Explanation: The Internet Control Message Protocol (ICMP) is used by ping to test connectivity between network hosts. The Address Resolution Protocol (ARP) is used to map IP addresses to MAC addresses. The Dynamic Host Configuration Protocol (DHCP) is used to dynamically assign IP addresses to network hosts. The Transmission Control Protocol (TCP) is considered a reliable protocol that segments the application layer data into segments for transmission.

9. A user issues a ping 2001:db8:3040:114::88 command and receives a response that includes a code of 3. What does this code represent?

  • port unreachable
  • host unreachable
  • protocol unreachable
  • network unreachable

Explanation: When a host or gateway receives a packet that it cannot deliver, it can use an ICMP Destination Unreachable message to notify the source that the destination or service is unreachable. The message will include a code that indicates why the packet could not be delivered. These are some of the Destination Unreachable codes for ICMPv4:

  • 0 : net unreachable
  • 1 : host unreachable
  • 2 : protocol unreachable
  • 3 : port unreachable

10. A user issues a ping 192.168.219.8 command and receives a response that includes a code of 0. What does this code represent?

  • protocol unreachable
  • network unreachable
  • host unreachable
  • port unreachable

Explanation: When a host or gateway receives a packet that it cannot deliver, it can use an ICMP Destination Unreachable message to notify the source that the destination or service is unreachable. The message will include a code that indicates why the packet could not be delivered. These are some of the Destination Unreachable codes for ICMPv4:

  • 0 : net unreachable
  • 1 : host unreachable
  • 2 : protocol unreachable
  • 3 : port unreachable

11. What characterizes a traceroute utility?

  • It is primarily used to test connectivity between two hosts.
  • It identifies the routers in the path from a source host to a destination host.
  • It sends four Echo Request messages.
  • It utilizes the ICMP Route Redirection messages.

Explanation: Traceroute is a utility that generates a list of hops (or routers) along the path from a source host to the destination host.

12. Why would a manager need to use the tracert command?

  • to display a list of the near-side router interfaces between the source device and the destination device
  • to query the Domain Name System (DNS) to get domain names and mapping information
  • to quickly verify connectivity by sending echo-request messages to the destination and receiving a series of echo-reply messages from that destination
  • to display a list of current processes running on a local or a remote computer

Explanation: Tracert is a utility that generates a list of hops that were successfully reached along the path. This list can provide important verification and troubleshooting information. If the data reaches the destination, then the trace lists the interface of every router in the path between the hosts. If the data fails at some hop along the way, the address of the last router that responded to the trace can provide an indication of where the problem or security restrictions are found.

13. Which protocol supports Stateless Address Autoconfiguration (SLAAC) for dynamic assignment of IPv6 addresses to a host?

  • UDP
  • ICMPv6
  • ARPv6
  • DHCPv6

Explanation: SLAAC uses ICMPv6 messages when dynamically assigning an IPv6 address to a host. DHCPv6 is an alternate method of assigning an IPv6 addresses to a host. ARPv6 does not exist. Neighbor Discovery Protocol (NDP) provides the functionality of ARP for IPv6 networks. UDP is the transport layer protocol used by DHCPv6.


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