How Traceroute Works
Every IP packet carries a TTL (Time To Live) value that each router decreases by one. When it reaches zero, the router drops the packet and usually sends an error message back. Traceroute uses this deliberately: it sends packets with TTL 1, 2, 3 and so on, and each router that reports an error reveals itself as a hop on the path.
Run one from our server with the Traceroute tool, or from your own computer:
tracert example.com (Windows)
traceroute example.com (macOS, Linux)Windows uses ICMP packets by default, while macOS and Linux traceroute use UDP by default. Some networks treat these differently, so results can vary between tools.
Reading Each Line
5 ae1.router.example.net (203.0.113.1) 12.4 ms 12.1 ms 12.9 ms- Hop number: the position on the path.
- Hostname and address: the router that answered. Hostnames often contain city or airport codes and the provider’s name. Look up unknown addresses with IP Location or ASN Lookup.
- Three times: round-trip times for three probes.
Asterisks Are Usually Harmless
A line of * * * means no reply arrived for that hop. Many routers do not send these error messages, or limit how many they send. If later hops answer normally, the silent hop is forwarding traffic fine. Only asterisks that continue until the end suggest that traffic stops somewhere — or that the destination simply does not answer traceroute probes, which is common for firewalled servers.
Latency Spikes in the Middle
Routers answer traceroute probes with low priority. A single hop showing high latency while the following hops are fast is not a problem; that router is just slow to reply to probes. A real problem looks different: latency rises at one hop and stays high for every hop after it.
Large jumps can also be physical: crossing an ocean adds tens of milliseconds because of distance alone.
Finding Where a Connection Really Fails
- Check whether the destination is reachable at all with Ping and Is My Site Down.
- Look for the first hop after which all hops are silent or slow.
- Identify that network’s owner; the problem is usually at or just after that point.
- Run traceroute from both sides if possible. Internet paths are often asymmetric, so the return path can differ from the outgoing path.
Private Addresses in the Path
The first hops often show private addresses such as 192.168.1.1 (your router) or 10.x.x.x and 100.64.x.x addresses inside your provider’s network. That is normal.