Traceroute
A tool that maps the hops a packet takes to a destination, exposing where delays or failures occur.
Traceroute works by sending packets with incrementally increasing Time-to-Live (TTL) values, starting at 1. Each router along the path decrements the TTL by 1; when it reaches 0, the router discards the packet and returns an ICMP Time Exceeded message, revealing its IP address and round-trip time. This builds a hop-by-hop map of the path to a destination, making it a go-to tool for isolating where latency spikes or packet loss begins. On the exam, note the platform difference: Windows uses tracert (ICMP echo requests), while Linux and macOS use traceroute (UDP probes to high ports by default). A key nuance is that an asterisk (*) does not always mean a failed router — many devices silently drop ICMP or UDP probes while still forwarding normal traffic.
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