Traceroute utility (known as tracert in Windows OS) tracks and prints the route packets taken on their way to a specified host or to an IP address and measures their transit delays.
While the ping command can determine if there is a problem, traceroute helps to identify where the problem exists. It prints the route packets trace to the network host.
This traceroute usually uses UDP echo packets to probe the route through the Internet from one device to another. It usually uses high UDP ports for tracing hosts. However, often the firewalls of the ISP providers block these UDP ports for security reasons.
We advise you to run the traceroute by including the ICMP echo flag when tracing a host or IP address:
-I, --icmp
Example:
tracert -I [hostname or IP address]
Usage
Traceroute is run from the Windows command prompt, from the Linux distros command line, or from the macOS Terminal app.
Windows
To run the tracert command in Windows press Windows+R to open the “Run” box. Type “cmd” and then click “OK” to open the Command Prompt. Run the tracert command followed by the address of the host. Note that tracert by default is using ICMP packets to probe the route.
tracert [hostname or IP address]
Linux
To run a traceroute command in Linux press Ctrl+Alt+T to open the Terminal window. Run the traceroute command followed by the address of the host.
traceroute -I [hostname or IP address]
macOS
To run a traceroute command in macOS press Control + Option + Shift + T to open a new Terminal window. Run the traceroute command followed by the address of the host.
traceroute -I [hostname or IP address]
Example:
$ traceroute -I ucdn.com
traceroute to ucdn.com (188.72.220.195), 30 hops max, 60 byte packets
1 184.170.253.126 113,215ms 113,273ms 113,035ms
2 98.142.220.60 112,893ms 113,004ms 113,103ms
3 38.122.14.121 113,584ms 113,652ms 113,304ms
4 154.54.81.25 114,159ms 114,348ms 113,976ms
5 154.54.30.186 180,025ms 180,160ms 180,159ms
6 154.54.56.94 187,623ms 318,430ms 187,665ms
7 154.54.56.166 193,894ms 193,503ms 193,418ms
8 149.11.202.26 198,873ms 200,900ms 194,585ms
9 78.140.169.239 194,010ms 193,363ms 195,771ms
10 188.72.220.195 193,675ms 193,244ms 193,252ms
Understanding the Output
traceroute test, by default, measures 30 hops of 60-byte packets.
traceroute to ucdn.com (188.72.220.195), 30 hops max, 60 byte packets
The first line of the traceroute output report what the command is doing – listing the destination host (ucdn.com), destination IP address (188.72.220.195), and the maximum number of hops that will be taken in the traceroute test (30).
The rest of the output shows the information on each hop on the path between the sender and the final destination.
1 184.170.253.126 113,215ms 113,273ms 113,035ms
2 98.142.220.60 112,893ms 113,004ms 113,103ms
3 38.122.14.121 113,584ms 113,652ms 113,304ms
4 154.54.81.25 114,159ms 114,348ms 113,976ms
5 154.54.30.186 180,025ms 180,160ms 180,159ms
6 154.54.56.94 187,623ms 318,430ms 187,665ms
7 154.54.56.166 193,894ms 193,503ms 193,418ms
8 149.11.202.26 198,873ms 200,900ms 194,585ms
9 78.140.169.239 194,010ms 193,363ms 195,771ms
10 188.72.220.195 193,675ms 193,244ms 193,252msThe first line presents your router (if you’re behind a router), the next lines represent your ISP, and each subsequent line represents a networking device that’s further away.
The format of each line is as follows:
hop [hostname/IP address] RTT1 RTT2 RTT3
hop:
The first column of the traceroute test shows the number of hops. The journey of each route that a packet takes to reach the next intermediary network device is called a hop. For example, in the output above, it takes 10 hops to reach the specified host (ucdn.com) from the location it has been run.
[hostname/IP address]:
The [hostname] or [IP address], helps you see the location of a router/network device.
RTT1, RTT2, RTT3:
This is the round-trip time that it takes for a packet to get to a hop and back to your device (shown in milliseconds). It is often referred to as latency. The traceroute sends three packets to each hop and displays each time.
The output of the traceroute may show asterisks [ * * * ] instead of the hostname and response times. The asterisks indicate that the target network device does not respond as the traceroute expected before the timeout occurred. This could be an indication of packet loss.