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Traceroute Output Interpreter

Read a traceroute or MTR properly — and stop blaming the hop that is not at fault.

What you paste

Parsed in your browser — never uploaded

Result

ISSUE

That could not be read

Paste the output of traceroute, tracert or MTR.

What this cannot tell you

  • Loss at an intermediate hop is only meaningful if it persists to the destination. Routers generate ICMP replies on their control plane and deprioritise that work when busy, so a hop can show 100% loss while forwarding every packet perfectly.
  • A destination that never replies is frequently normal rather than a fault — a great many hosts and firewalls drop traceroute probes by policy while serving traffic fine.
  • Shows the path at the moment the trace ran, in one direction. The return path can differ entirely and is not visible from here.
  • Traceroute output carries no loss percentage; only MTR reports one. On a plain traceroute the loss analysis has less to work with.
  • Parsed in your browser. Nothing is uploaded, and the output you paste is not stored.

Take this with you

How this reads your output

Traceroute, Windows tracert and MTR output are all accepted, because they answer the same question and are misread in the same way. The analysis is built around one rule: loss at hop N counts only if it is still there at the destination. Routers build ICMP replies on the slow path — the control plane rather than the forwarding hardware — and they rate-limit or drop that work whenever they are busy, so a middle hop showing complete loss while passing your traffic untouched is entirely ordinary. Highlighting it is how people end up complaining to a provider about a router that is working correctly. Latency is treated the same way: a spike at one hop that falls again afterwards is that router answering slowly, and only a rise that carries through to the end is on the path.

What the results mean

Loss reaching the destination
The only loss that describes your connection. Everything else is a reporting artefact.
Middle-hop loss
A router deprioritising its own ICMP replies. Not a fault, and the most misread result there is.
Sustained latency rise
Rose and stayed risen. Real added distance or congestion, usually a long-haul link or a peering point.
Destination did not reply
Common and weakly informative. Many hosts drop these probes deliberately.

Common problems and fixes

Hop 3 shows 100% loss — is that my problem?
Almost certainly not, if the destination is answering. That router is rate-limiting its ICMP replies while forwarding your packets normally.
The trace stops before the destination
Usually a firewall or the host itself declining to answer. Check whether the actual service responds before concluding anything.
Latency jumps at one hop then drops again
That router answered slowly. Only a rise that persists to the final hop is on the path.

Frequently asked questions

Why does a middle hop show packet loss when everything works?

Because routers generate ICMP replies on their control plane rather than in forwarding hardware, and deprioritise that when busy. Replying to you is optional work; forwarding your traffic is not. So a hop can lose every probe and pass every packet.

Does a traceroute show the return path?

No, and this catches people out. It shows the outbound path only, and internet routing is frequently asymmetric — the return path can be entirely different and is where the problem sometimes lives.

Should I send a traceroute to my ISP?

Yes, and send the whole thing with the destination reachable. Point at the hop where loss to the destination begins rather than at the worst-looking line, which is the part support teams most often have to correct.

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