12.3.4 ICMP Quiz Answers

Networking Devices and Initial Configuration Module 12.3.4 ICMP Quiz Answers

1. A technician uses the ping 127.0.0.1 command. What is the technician testing?

  • the TCP/IP stack on a network host
  • connectivity between two adjacent Cisco devices
  • connectivity between a PC and the default gateway
  • connectivity between two PCs on the same network
  • physical connectivity of a particular PC and the network

Explanation: 127.0.0.1 is the local loopback address on any TCP/IP network device. By pinging this address, the technician is verifying the TCP/IP protocol stack on that particular device.

2. Which command can be used to test connectivity between two devices using echo request and echo reply messages?

  • netstat
  • ipconfig
  • ICMP
  • ping

Explanation: Ping is used to test connectivity between end devices. It can be used with both IPv4 and IPv6. Ping uses the ICMP protocol which issues an echo request/echo reply. The ipconfig command is used at the command line of a Windows computer to display IP addressing information. Netstat is used to display the local routing table.

3. What field content is used by ICMPv6 to determine that a packet has expired?

  • TTL field
  • CRC field
  • Hop Limit field
  • Time Exceeded field

Explanation: ICMPv6 sends a Time Exceeded message if the router cannot forward an IPv6 packet because the packet expired. The router uses a hop limit field to determine if the packet has expired, and does not have a TTL field.

4. Which protocol provides feedback from the destination host to the source host about errors in packet delivery?

  • ARP
  • BOOTP
  • DNS
  • ICMP

Explanation: The ICMP protocol operates at Layer 3 of the OSI model, which is the Internet layer of the TCP/IP model. ICMP encapsulates the ping and traceroute commands.

5. What mechanism is used by a router to prevent a received IPv4 packet from traveling endlessly on a network?

  • It checks the value of the TTL field and if it is 0, it discards the packet and sends a Destination Unreachable message to the source host.
  • It checks the value of the TTL field and if it is 100, it discards the packet and sends a Destination Unreachable message to the source host.
  • It decrements the value of the TTL field by 1 and if the result is 0, it discards the packet and sends a Time Exceeded message to the source host.
  • It increments the value of the TTL field by 1 and if the result is 100, it discards the packet and sends a Parameter Problem message to the source host.

Explanation: To prevent an IPv4 packet to travel in the network endlessly, TCP/IP protocols use ICMPv4 protocol to provide feedback about issues. When a router receives a packet and decrements the TTL field in the IPv4 packet by 1 and if the result is zero, it discards the packet and sends a Time Exceeded message to the source host.

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

  • ARP
  • DHCP
  • TCP
  • ICMP

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.

7. A user is executing a tracert to a remote device. At what point would a router, which is in the path to the destination device, stop forwarding the packet?

  • when the router receives an ICMP Time Exceeded message
  • when the RTT value reaches zero
  • when the host responds with an ICMP Echo Reply message
  • when the value in the TTL field reaches zero
  • when the values of both the Echo Request and Echo Reply messages reach zero

Explanation: When a router receives a traceroute packet, the value in the TTL field is decremented by 1. When the value in the field reaches zero, the receiving router will not forward the packet, and will send an ICMP Time Exceeded message back to the source.

8. Which protocol is used by the traceroute command to send and receive echo-requests and echo-replies?

  • SNMP
  • ICMP
  • Telnet
  • TCP

Explanation: Traceroute uses the ICMP (Internet Control Message Protocol) to send and receive echo-request and echo-reply messages.

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

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

10. Which ICMPv6 message type provides network addressing information to hosts that use SLAAC?

  • neighbor solicitation
  • router advertisement
  • neighbor advertisement
  • router solicitation

Explanation: IPv6-enabled router interfaces send periodic router advertisement messages that provide addressing information to hosts that perform SLAAC.

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

12. A user issues a ping 198.51.100.25 command and receives a response that includes a code of 2. 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

Subscribe
Notify of
guest

3 Comments
Inline Feedbacks
View all comments
Mohd. Rizky Nasution (Kiky)
Mohd. Rizky Nasution (Kiky)
8 months ago

number 6 ask the protocol not the command. So the answer is ICMP

Zimou
Zimou
9 months ago

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

  • ICMP
3
0
Would love your thoughts, please comment.x
()
x