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.
When using the Tracert command, a UDP packet with a TTL (Time To Live) value is sent to the destination. As the packet traverses each router, the TTL is decremented by one. When the TTL reaches zero, the router sends back an ICMP Time Exceeded message to the source device to indicate that the packet has been discarded. This mechanism helps in identifying the path taken by the packet and locating the intermediate routers in the network.
D. I think the question is a bit odd at the end. '' The TTL turns to 0 when the packets arrive at RTA, upon which RTA sends an ICMP Port unreachable message to the source device.