What Is a Traceroute?

For most of us, phone calls and Internet connections seem to happen instantaneously. It feels as if our computer has a direct line to our favorite websites. Web pages load so fast that it seems that we must have a direct connection to any computer, even one across the country.

But we don’t.

Not since a kid connected a tomato can to his friend’s tomato can with a piece of string—and had a “phone” conversation—have we had those kinds of direct connections.

When you’re on the Internet, information or requests sent from your computer don’t reach the destination computer in a single jump. In fact, it takes a number of computers, networked together, to help you receive and transmit information. Your data requests and replies take unique routes along the Internet.

Sometimes people want to know what that route is, and that’s where the concept of traceroute comes in.

Traceroute defined.

Quite simply, a traceroute procedure allows you to find out precisely how a data transmission (like a Google search) traveled from your computer to another. Essentially, the traceroute compiles a list of the computers on the network that are involved with specific Internet activity.

The traceroute identifies each computer/server on that list and the amount of time it took the data to get from one computer to the next. If there was a hiccup or interruption in the transfer of data, the traceroute will show where along the chain the problem occurred.

Aside from being somewhat interesting, performing a traceroute also has a very practical use: If someone is having difficulty accessing a particular website or computer, performing a traceroute can help find out where the problem is occurring along the network.

How data travels.

Each computer on the traceroute is identified by its IP address, which is the nine-digit number separated by periods that identifies that computer’s unique network connection.

Here are a few details regarding a traceroute:

• The journey from one computer to another is known as a hop.
• The amount of time it takes to make a hop is measured in milliseconds.
• The information that travels along the traceroute is known as a packet.

A traceroute readout typically will display three separate columns for the hop time, as each traceroute sends out three separate packets of information to each computer. At the very top of the list, the traceroute will give the limit of how many lines of hops it will display—30 hops is often the maximum number.

When a traceroute has difficulty accessing a computer, it will display the message “Request timed out.” Each of the hop columns will display an asterisk instead of a millisecond count.

Hackers at the hop.

On occasion, a traceroute will show one hop time, with the next two columns displaying asterisks. This usually indicates that although the computer accepted one packet, the other two packets were discarded. This isn’t unusual—because of security concerns, many computers routinely reject multiple packages, or forward them to different sources.

In the past, computer hackers would routinely use traceroutes to map how information moved within a company’s computer network and then focus their attacks on certain computers. To combat that security threat, some networks will not allow you to perform a traceroute.

How to run a traceroute.

On a PC using Windows, you can perform a traceroute using the traceroute utility on the Windows operating system (as long as you are not attempting to tap into heavily secured networks). You’ll need to know the domain name, IP address, or name of the specific computer you’re trying to reach.

Using the traceroute utility, you would type “tracert x“—where “x” stands for the IP address, the domain name or the computer name.

If using Macintosh OS X or any subsequent versions, you may use either the Terminal program or the network utility to generate a traceroute. The utility will display the traceroute on your screen.

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