How to perform and read a traceroute on Linux and Windows
To run traceroute on a Linux system, do the following:
- Open up an instance of Terminal.
- Type in the phrase “traceroute [hostname]” and press enter.
On a Windows system, you can:
- Go to the Start menu.
- Select Run.
- Type in “cmd” and then hit “OK.” This initiates a command prompt.
- Type in “ tracert [hostname]” and press enter.
The term “hostname” or host is the website you are interested in or the IP address of a server, router, or device. The traceroute reports on this destination point. After the traceroute is done, it terminates on its own.
What is traceroute?
A traceroute provides a map of how data on the internet travels from your computer to its destination.
How does traceroute work?
A traceroute works by sending Internet Control Message Protocol (ICMP) packets, and every router involved in transferring the data gets these packets. The ICMP packets provide information about whether the routers used in the transmission are able to effectively transfer the data.
What is traceroute used for?
Running traceroute is helpful for figuring out the routing hops data has to go through, as well as response delays as it travels across nodes, which are what send the data toward its destination. Traceroute also enables you to locate points of failure.
What is the difference between ping and traceroute?
The primary difference between ping and traceroute is that while ping simply tells you if a server is reachable and the time it takes to transmit and receive data, traceroute details the precise route, router by router, as well as the time it took for each hop.
How To Read a Traceroute Report
Hops and Round Trip Times (RTT)
The traceroute report lists data pertaining to every router the packets pass through as they head to their destination. The hops get numbered on the left side of the report window. Each line in the report has the domain name—if that was included—as well as the IP address belonging to the router.
There are also three measurements of time, displayed in milliseconds. These tell you the length of time to send the ICMP packets from your computer to that router and back.
Typical Hop Sequence
A “hop” refers to the move data makes as it goes from one router to the next. The first hop within the report provides information about the first router, which would be on your local-area network (LAN). The hops that come after provide data about routers controlled by your internet service provider (ISP).
When the ICMP packets get beyond the ISP’s domain, they go to the general internet, and you will likely see that the hop times increase, typically due to geographical distance.
Do You See an Asterisk? What Does It Mean?
Sometimes, a traceroute has a hard time accessing a device or is unreachable. In these situations, it may show a message saying, “Request timed out,” along with an asterisk. This indicates that the router it reached was configured to deprioritize or automatically reject ICMP packets, which is done because ICMP is not categorized as essential traffic by many routers.
If you get several timeouts in a row, it can be because:
- The packets arrived at a router with a firewall that prevents traceroute online requests.
- The packets arrived at the subsequent router, but they were not able to return to the computer that sent them.
- The router has a connection problem.