What is traceroute and how does it work?
Traceroute reveals the path packets take by sending probes with gradually increasing hop limits. Each router that expires the packet can return a message, creating a hop-by-hop view of the route.
- Why traceroute shows multiple hops.
- Why the path out and back may differ.
- Why stars do not always mean an outage.
The TTL method
Traceroute relies on hop limits such as TTL or IPv6 Hop Limit.
Each probe expires one hop farther along the path until the destination responds or the max is reached.
What the hops mean
Each line is usually a router or policy boundary that answered the probe.
Large jumps in latency can help highlight congestion or distance, but only if they persist on later hops too.
Why results can look strange
Routers may rate limit or ignore traceroute probes.
Some MPLS, tunnels, NAT, or firewalls make the visible path different from the forwarding path.
How to use it well
Look for patterns that continue forward, not just one isolated slow hop.
Combine traceroute with ping and DNS checks for a fuller picture.
Why do I see stars?
Because some devices do not answer traceroute probes even while they forward traffic.
Can traceroute prove the problem router?
Not always. It is a clue, not a perfect verdict.
Last updated: March 29, 2026