Why traceroute shows stars or timeouts
Traceroute stars usually mean a router did not answer that probe in time. They do not automatically mean the router dropped your production traffic.
- Why intermediate routers may ignore probes.
- How to spot the difference between noise and a real problem.
- What patterns matter most in a traceroute.
Rate limits
Routers often protect their control plane by limiting how often they answer TTL-expired probes.
That can produce stars or inconsistent latency even while forwarding continues normally.
Asymmetry and MPLS
The path back for the control response may differ from the forward path you are tracing.
Overlay and MPLS designs can also hide parts of the path.
What to look for
If loss begins at one hop and continues through later hops, it is more meaningful.
If one hop looks bad but later hops recover, that hop is often only rate-limiting replies.
Better diagnosis
Repeat tests from more than one vantage point.
Combine traceroute with ping and application checks before assigning blame.
Are stars always bad?
No. They are very common and often harmless.
Can the last hop timeout even if the service is reachable?
Yes. Some destinations refuse to answer traceroute probes directly.
Last updated: March 29, 2026