How to Read Traceroute Output: A Hop-by-Hop Guide
A traceroute shows you the path your traffic takes across the internet, one router at a time. The output can look intimidating, but every column means something specific. This guide walks through what each part of a traceroute (or tracert on Windows) tells you, and how to read it without jumping to the wrong conclusion. You can run one yourself with our visual traceroute tool.
What a Traceroute Is Actually Showing
Each line in a traceroute is one hop, a single router along the path between you and the destination. Traceroute discovers these routers by sending packets with a deliberately small Time To Live (TTL) value and reading the TTL-exceeded messages that routers send back when the TTL reaches zero. Each hop is just a router doing its normal job of forwarding packets and decrementing the TTL. For the underlying mechanism, see traceroute vs ping vs mtr.
Reading the Columns
A typical line has four parts: the hop number, three round-trip times (RTTs), and the hostname and IP address of the router that replied. Traceroute sends three probes per hop by default, so you see three latency measurements, which helps you tell a steady result from a noisy one. Many routers have no PTR record, so you may see only an IP, which is completely normal.
Step 1: Read Top to Bottom as a Journey
The first hops are usually your own router and your ISP local network. The middle hops are transit and backbone routers. The last hop is the destination host. Reading downward, you are following the packet journey from your network to the target.
Step 2: Look for Where Latency Jumps and Stays High
Do not focus on any single hop number in isolation. Instead, look for the point where RTT increases and stays elevated for every hop afterward. A jump that persists to the destination usually marks a real change, for example crossing a long-distance link or congestion at a specific point.
Step 3: Ignore a Single High Middle Hop That Recovers
If one middle hop shows a high RTT but the hops after it, including the destination, are fast again, that is normal and not a problem. The router at that hop is simply deprioritizing the replies it has to answer itself. Latency only matters when it appears at the destination or persists through every later hop. If a hop shows nothing but asterisks, see why is my traceroute timing out.
Spotting the Real Problem Hop
A genuine problem looks like latency that rises at one hop and remains high through to the end, or a destination that never replies at all. Use the destination behavior as your ground truth: if the final hop responds quickly, the path is healthy regardless of what individual middle hops show.
Frequently Asked Questions
What do the three numbers in a traceroute mean?
Traceroute sends three probe packets to each hop by default, so the three numbers are three separate round-trip time measurements in milliseconds. Seeing three values lets you judge whether a hop is consistently slow or just had one noisy probe. If all three are similar, the measurement is stable.
Why does one hop show high latency but the destination is fast?
That middle router is deprioritizing the replies it generates for traceroute, because answering probes is low-priority work compared to forwarding real traffic. The high number reflects how slowly that router answers, not how slowly it forwards data. Because later hops and the destination are fast, the path is fine.
What does a star or asterisk mean in traceroute?
An asterisk means traceroute did not receive a reply from that hop within the timeout. It often means the router is configured not to answer probe packets, which is a policy choice and not a fault. Asterisks at middle hops are usually harmless, while no reply at the final destination points to a real reachability problem.
How do I know which hop is causing the problem?
Look for the hop where latency rises and stays elevated through every later hop, or for a destination that never responds. A single slow middle hop that recovers afterward is not the cause. The destination response is the most reliable signal of whether the path is healthy.
What is a hop in a traceroute?
A hop is one router on the path between you and the destination. Each hop forwards your packet onward and reduces its Time To Live value by one. Traceroute reveals each hop by reading the TTL-exceeded message a router sends when the value reaches zero.