Traceroute

Traceroute maps the network path that packets take from the source to a destination host, listing each intermediate router (hop) along the way and the round-trip time to reach it. It reveals how many hops separate you from the target and where in the journey latency spikes or packets get dropped, making it the go-to tool for diagnosing where a connection slows down or breaks. Each line in the output represents one hop closer to the destination.

The classic technique works by sending packets with incrementally increasing TTL (Time To Live) values; each router that decrements the TTL to zero returns an ICMP "time exceeded" message, revealing its address and timing. By stepping the TTL from 1 upward, traceroute discovers the routers one by one until the destination is reached. Implementations may use ICMP, UDP, or TCP probes depending on what intermediate networks permit.

Use cases include diagnosing routing problems, identifying which network segment introduces latency, confirming that traffic takes an expected geographic path, and gathering evidence when reporting an issue to an ISP or hosting provider. It complements a Ping Test, which tells you the end-to-end latency, by breaking that latency down hop by hop, and works alongside DNS and Hosting Provider tools to understand the infrastructure at the far end.

Interpret the output carefully: asterisks or timeouts at a hop usually mean that router declines to reply to probes, not that the path is broken, since traffic often passes through silent hops just fine. Latency that rises and then stabilizes across later hops is normal, while a sustained jump that persists to the destination flags the likely bottleneck. Because the internet uses asymmetric routing, the return path may differ from the outbound path you see.