If a network condition prevents traceroute from reaching the destination

Common reasons for traceroute failing to reach a destination include:

  • Timeouts (indicated by one asterisk per probe, per hop)

  • Unreachable hosts

  • Unreachable networks

  • Interference from firewalls

  • Hosts configured to avoid responding

Executing traceroute where the route becomes blocked or otherwise fails results in an output marked by timeouts for all probes beyond the last detected hop. For example, with a maximum hop count of 7 (maxttl = 7), where the route becomes blocked or otherwise fails, the output appears similar to this:

Figure 161: Traceroute failing to reach the destination address