Traceroute for Mac

$ traceroute example.com

What it’s for

Traceroute shows the path your traffic takes to a host: every router on the way, called a hop, in order, with the time each one takes to answer. It tells you how far your traffic gets, and where on the way the delay is added.

Use it when

• A site is slow or can’t be reached, and you want to see how far the path gets.
• You want to know which networks carry your traffic.
• You are reporting a problem and need to show the route.

Reading the result

The probes for a hop go out together, so a silent hop costs one timeout, not three. When several routers answer for the same hop, as on a load-balanced path, all of their addresses are listed. Names appear a moment later, as their lookups finish.

What you might see

• Stars from some hop to the end, and “destination does not respond to ICMP”. The host, or a firewall in front of it, ignores traceroute probes. If the site works, nothing is wrong.
• “A router reports the destination unreachable”: the trace stopped because a router on the way has no route to the host.
• The first hop is already slow. That is your Wi-Fi or your router. See Wi-Fi Analyzer.

Options worth knowing

• Max hops: how far to look, up to 64.
• Probes: one to three per hop.
• Timeout: how long to wait for each hop.
• Look up providers names the network each address belongs to.

Related

• MTR keeps probing the same path, which shows loss a single trace misses.
• Visual Traceroute draws the route on a map.
• Hops and TTL, how a route is discovered.