How to trace network routes with traceroute

· Category: Networking

Short answer

Traceroute traces the route packets take from your device to a destination. It reveals each intermediate hop and measures latency at each step.

Steps

  1. Run the command: Use tracert on Windows or traceroute on Linux and macOS followed by the target IP or domain.

  2. Read the output: Each line represents a hop. Three latency measurements are shown per hop.

  3. Identify anomalies: - Asterisks (*) indicate timeouts, often due to ICMP rate limiting. - Sudden latency jumps suggest congestion or a distant geographic hop. - Repeating addresses may indicate routing loops.

  4. Compare directions: Test from multiple locations to distinguish local issues from backbone problems.

Tips

  • Use traceroute -I for ICMP mode or -T for TCP SYN mode if UDP is blocked.
  • High latency at the first hop usually indicates local network congestion.
  • Private IPs appearing mid-trace are normal for carrier MPLS networks.

Common issues

  • Firewalls blocking probe packets causing incomplete traces.
  • Load-balanced paths showing inconsistent hop ordering.
  • Misinterpreting * timeouts as packet loss rather than filtering.