Huawei Certified Network Associate – Routing and Switching (HCNA-RS, legacy) — Question 103

There are two routers (RTA and RTB) between the source device and destination device. The Tracert command is used to detect the path between the two devices. During detection of the first hop (RTA), the source device sends a UDP packet with a TTL of 1 to an interface with a large interface number on the destination device. The TTL turns to 0 when the packet arrives at RTB, upon which RTA sends an ICMP ______ message to the source device.

Answer options

• A. Time Exceeded.
• B. Echo Request.
• C. Echo Reply.
• D. Port Unreachable.

Correct answer: A

Explanation

The correct answer is A, 'Time Exceeded,' because when the TTL reaches 0, the router sends this message back to indicate that the packet could not be forwarded. The other options, such as 'Echo Request' and 'Echo Reply,' are part of the ping process and do not apply in this scenario, and 'Port Unreachable' is used when a packet arrives at a closed port, which is not relevant here.