traceroute – trace packet route to host
traceroute shows the path packets take to reach a network host, displaying each hop along the way.
Synopsis
traceroute [OPTIONS] HOST
Examples
Basic traceroute
$ traceroute google.com
traceroute to google.com (142.250.187.206), 30 hops max
1 router (192.168.1.1) 1.234 ms 1.123 ms 1.012 ms
2 isp-gateway (10.0.0.1) 5.678 ms 5.432 ms 5.321 ms
3 core-router (203.0.113.1) 12.345 ms 11.234 ms 10.123 ms
...
10 google.com (142.250.187.206) 15.678 ms 14.567 ms 13.456 ms
Use ICMP (requires root)
$ sudo traceroute -I google.com
Use TCP
$ sudo traceroute -T -p 443 google.com
Numeric only (no DNS)
$ traceroute -n google.com
Set max hops
$ traceroute -m 15 google.com
Understanding Output
3 core-router (203.0.113.1) 12.345 ms 11.234 ms 10.123 ms
│ │ │
│ │ └─ Round-trip times (3 probes)
│ └─ IP address (and hostname)
└─ Hop number
- * * *: No response (firewall, timeout)
- !H: Host unreachable
- !N: Network unreachable
mtr: Better Alternative
mtr combines ping and traceroute:
$ mtr google.com
Common Options
| Option | Description |
|---|---|
-n | No DNS resolution |
-I | Use ICMP (like ping) |
-T | Use TCP |
-p PORT | Destination port |
-m N | Max hops |
-w N | Wait time |
Tips
- Asterisks are common: Many routers don’t respond to traceroute
- Use mtr for live view: Better for diagnosing intermittent issues
- TCP for firewalled hosts:
-T -p 80or-T -p 443 - macOS: Uses UDP by default (like Linux)
