What Is Traceroute? Mapping the Path Your Packets Take

Traceroute (or tracert on Windows) is a network diagnostic tool that shows the path packets take from your computer to a destination, listing every router hop along the way with the round-trip time for each. When you’re trying to figure out why a website is slow, where packets are getting dropped, or which network is causing latency, traceroute gives you visible proof of the exact route your traffic is taking across the internet.

How Traceroute Works

Traceroute exploits how the TTL (Time to Live) field in IP packets works. Every packet has a TTL value that decrements by 1 at each router. When TTL reaches 0, the router drops the packet and sends back an ICMP “Time Exceeded” message. Traceroute uses this behavior cleverly:

1. Send a packet with TTL=1. The first router drops it and sends back its identity.
2. Send a packet with TTL=2. The second router drops it and identifies itself.
3. Send a packet with TTL=3. Third router responds.
4. Continue until the destination is reached.

Each hop reveals its IP address and the round-trip time of the probe. The result is a complete map of the path.

Reading Traceroute Output

 1    1ms    1ms    1ms    192.168.1.1        [Your Router]
 2   12ms   11ms   12ms    10.0.0.1           [ISP Gateway]
 3   15ms   14ms   15ms    72.14.215.69       [ISP Core Router]
 4   32ms   31ms   33ms    108.170.252.1      [Google Edge]
 5   35ms   34ms   35ms    142.250.80.46      [Destination]

Each line shows: hop number, three latency measurements (to catch variance), and the router’s IP. Dramatic latency increases between hops indicate a likely bottleneck. If hop 3 is 15ms and hop 4 is 120ms, the link between those routers is adding 105ms of latency.

Running Traceroute

Windows: tracert google.com Mac/Linux: traceroute google.com Alternative (better): mtr google.com (combines ping and traceroute with continuous updates)

MTR (My Traceroute) is particularly useful because it runs continuously, showing real-time statistics for each hop, making intermittent issues easier to spot.

Test It Yourself

Frequently Asked Questions