Exploring Network Paths with traceroute
traceroute
Traceroute is a diagnostic tool that reveals responding routers along a path and the time taken to receive their replies. If communication fails, an overloaded or faulty intermediate node is one possible explanation. A trace provides evidence for investigating the path, but does not by itself identify exactly where ordinary application packets were lost.
Traceroute sends probes with successively larger hop limits. When a probe expires at a router, the router may return a response that identifies it. Typical implementations send three probes per hop limit. Different probe types and filtering policies can affect which responses appear.
traceroute (Linux) / tracert (Windows)
tracert www.github.comExample Output
| Hop | RTT 1 | RTT 2 | RTT 3 | Router / host |
|---|---|---|---|---|
| 1 | 2 ms | 9 ms | 2 ms | HS8145V [192.168.1.1] |
| 2 | 5 ms | 15 ms | 5 ms | 100.65.0.1 |
| 3 | 5 ms | 5 ms | 5 ms | 124.74.22.41 |
| 4 | 25 ms | 6 ms | 17 ms | 101.95.88.138 |
| 5 | * | * | * | Request timed out |
| 6 | * | * | * | Request timed out |
| 7 | * | * | * | Request timed out |
| 8 | 30 ms | 32 ms | 35 ms | 106.38.244.146 |
| 9 | * | * | * | Request timed out |
| 10 | * | * | * | Request timed out |
| 11 | * | * | * | Request timed out |
| 12 | 30 ms | 31 ms | 31 ms | 220.181.38.251 |
KNOWLEDGE QUIZ
KNOWLEDGE QUIZ
Read a trace without overclaiming
Compute the mean RTT for R1 and the target. Does the silent second hop prove a complete forwarding failure? Is the target's mean RTT a one-way delay? Give one supported conclusion and one conclusion that the trace cannot establish.
| Hop | RTT 1 | RTT 2 | RTT 3 | Responder |
|---|---|---|---|---|
| 1 | 2 ms | 3 ms | 4 ms | R1 |
| 2 | * | * | * | — |
| 3 | 15 ms | 18 ms | 21 ms | R3 |
| 4 | 20 ms | 21 ms | 22 ms | Target |