"traceroute" - Trace Routes to Remote Host

Linux Tutorials - Herong's Tutorial Examples

∟"traceroute" - Trace Routes to Remote Host

This section provides a tutorial example on how to use 'traceroute' command to trace routes (or gateways) between the local host and a given remote host.

"traceroute" is a command line tool that allows to trace routes (or gateways) between the local host and a given remote host. "traceroute" utilizes the IP protocol "TTL (Time To Live)" field and attempts to elicit an ICMP TIME_EXCEEDED response from each gateway along the path to some host.

Here is an example of the "traceroute" command that shows all gateways behave nicely and sent back correct ICMP "time exceeded" messages.

herong$ traceroute nis.nsf.net

traceroute to nis.nsf.net (35.1.1.48), 30 hops max, 38 byte packet

1 helios.ee.lbl.gov (128.3.112.1) 19 ms 19 ms 0 ms
2 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 39 ms 19 ms
3 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 39 ms 19 ms
4 ccngw-ner-cc.Berkeley.EDU (128.32.136.23) 39 ms 40 ms 39 ms
5 ccn-nerif22.Berkeley.EDU (128.32.168.22) 39 ms 39 ms 39 ms
6 128.32.197.4 (128.32.197.4) 40 ms 59 ms 59 ms
7 131.119.2.5 (131.119.2.5) 59 ms 59 ms 59 ms
8 129.140.70.13 (129.140.70.13) 99 ms 99 ms 80 ms
9 129.140.71.6 (129.140.71.6) 139 ms 239 ms 319 ms
10 129.140.81.7 (129.140.81.7) 220 ms 199 ms 199 ms
11 nic.merit.edu (35.1.1.48) 239 ms 239 ms 239 ms

As you can see from the above output,

The first number on each output line indicates how many hops (or gateways) away from the local host.
For each gateway, "traceroute" triggers 3 ICMP "time exceeded" messages.
The last 3 time measurements are waiting times for those 3 returning ICMP "time exceeded" messages.
Obviously, the waiting time is longer, if the gateway is further away from the local host.

Here is another example of the "traceroute" command that shows some gateways behave badly. They either didn't send ICMP "time exceeded" messages or sent them with a TTL too small to reach the localhost. Those badly behaved gateways are identified by "* * *".

herong$ traceroute google.com

traceroute to google.com (172.217.31.206), 30 hops max, 60 byte packets
1 gateway (192.168.0.1) 2.050 ms 3.041 ms 2.819 ms
2 10.234.0.1 (10.234.0.1) 3.771 ms 3.749 ms 3.716 ms
3 * * *
4 * * *
5 * * *
6 14.140.100.6 (14.140.100.6) 12.234 ms 13.070 ms 12.644 ms
7 * * *
8 * * *
9 108.170.253.97 (108.170.253.97) 11.451 ms 108.170.253.113
10 74.125.253.13 (74.125.253.13) 9.523 ms 11.963 ms 11.388 ms
11 172.217.31.206 (172.217.31.206) 10.477 ms 10.222 ms 8.391 ms