Trace Route (traceroute) is a computer network tool used to determine the route taken by packets across an IP network.

Traceroute works by increasing the "time-to-live" value of each successive batch of packets sent. The first three packets sent have a time-to-live (TTL) value of one (implying that they are not forwarded by the next router and make only a single hop). The next three packets have a TTL value of 2, and so on. When a packet passes through a host, normally the host decrements the TTL value by one, and forwards the packet to the next host. When a packet with a TTL of one reaches a host, the host discards the packet and sends an ICMP time exceeded (type 11) packet to the sender.

The traceroute utility uses these returning packets to produce a list of hosts that the packets have traversed en route to the destination. The three timestamp values returned for each host along the path are the delay (aka latency) values typically in milliseconds (ms) for each packet in the batch. If a packet does not return within the expected timeout window, a star (asterisk) is traditionally printed. Traceroute may not list the real hosts. It indicates that the first host is at one hop, the second host at two hops, etc. IP does not guarantee that all the packets take the same route. Also note that if the host at hop number N does not reply, the hop will be skipped in the output.

The w3dt Trace Route tool is based off the unix/linux command "TRACEROUTE".