CISCO CCNA 200-301 Q159

You execute the ping command from a host, but the router does not have a path to its destination. Which of the following ICMP message types will a client receive from the router?

A. ICMP redirect
B. ICMP time exceeded
C. ICMP destination unreachable
D. ICMP echo-reply

Correct Answer: C

When a router receives a ping packet and has no route to the destination in its routing table, it will respond to the client with an ICMP destination-unreachable message. Internet Control Message Protocol (ICMP) is a Layer 3 protocol used to test the connectivity between hosts in a network.

There are six types of unreachable destination message:
1. Network unreachable
2. Host unreachable
3. Protocol unreachable
4. Port unreachable
5. Fragmentation needed and Don’t Fragment (DF) bit set
6. Source route failed

An ICMP redirect message would not be received. This type of response is received when the router is configured to direct clients to a different router for better routing.

An ICMP time-exceeded message would not be received. This type of response occurs when the router successfully sent the packet but did not receive an answer within the allotted time; in other words, the time-to-live of the ICMP packet has been exceeded.

An ICMP echo-reply message would not be received. This would be the response received if the destination received the ping command and responded successfully.