Guide
What traceroute shows
Traceroute is a list of routers that were willing to answer “this packet’s time-to-live expired.” Timeouts in the list are normal, not always a break.
Why you should care
When a site is slow, traceroute hints whether delay starts near you, in the middle of the internet, or near the destination.
It is a map of one direction from one vantage point, not a guarantee of the return path.
How hops are discovered
Each probe uses a larger time-to-live (TTL). Routers that decrement TTL to zero should announce themselves. The destination eventually answers if it allows the probe type.
Stars or timeouts mean nobody answered that TTL. Traffic may still flow through that router.
Visible hop
A router sent a TTL-expired message
- Probe
- Router replies
- You see the hop
Hidden hop
Many routers stay silent on purpose
- Probe
- Router ignores ICMP/UDP
- Timeout (*)
Reading a latency jump
A sudden RTT increase often marks the segment where delay begins. Later hops with similar RTT are not each adding that much again — the clock is still round-trip from the start.
ICMP priority can make intermediate hops look worse than real user traffic.
How to check
Run traceroute to a host, then ping the same name. Use both as clues, not as a single verdict.
Remember an online traceroute is from the tool provider, not from your house.
Remember
- Paths are often asymmetric.
- Timeouts are common and not always a fault.
- Online traces are not your ISP path.
- Firewalls can hide hops while still forwarding packets.
