Using traceroute

For starters, let’s pose these questions: Where do all those packets really go when we send them over the Internet? And, how do all the packets actually get to their destinations? Well, we can use the TCP/IP traceroute (tracert with Windows) command-line utility to help us answer both questions because its output will show us every router interface a TCP/IP packet passes through on the way to its destination.

Traceroute (trace for short) displays the path a packet takes to get to a remote device in all its glory by using something we call IP packet Time to Live (TTL) time-outs and Internet Control Message Protocol (ICMP) error messages. And it’s also a handy tool for troubleshooting an internetwork because we can use it to figure out which router along a path through that internetwork happens to be causing a network failure when a certain destination machine or network is, or suddenly becomes, unreachable.

To use tracert, at a Windows command prompt, type...