Traceroute, or commonly referred to as TRACERT, is a command line program that assists you in troubleshooting network connectivity issues from your Destination to a Remote destination by using echo packets (ICMP) to visually trace the route.
Within these echo packets, traceroute uses IP Time-To-Live (TTL) values of varying times. As the packet hops from one router to router through to get to its destination, each router is required to decrement the echo packets TTL by a minimum of 1 before proceeding to forward the packet to the next router. In other words, Time-To-Live is a Hop Counter by design.
When the Time-To-Live value reaches 0 (zero), the router then sends an ICMP message called “TIME EXCEEDED” to the source computer.
Traceroute works in the way of sending the 1st Echo packet with a Time-To-Live of 1 and subsequently will increment each additional Time-To-Live packet by 1 until the destination responds or the maximum Time-To-Live is reached. When an intermediate router sends back a “TIME EXCEEDED” message, you'll then see the route printed on the screen. This is how Traceroute works in its simplest form. You will see a list of intermediate routers/hops until the packet reaches its destination in which it returns an ICMP Echo Reply packet.
Traceroute will then show you a List of all intermediate jumps (which are all routers the packet has gone through) along with IP Addresses and Latency (delay) Values in Milliseconds for each hop. This MS delay is derived from the Timestamp values returned from each router along the path.
The originating sender of the packet expects a reply within a given amount of seconds. If there is no acknowledgment, then an Asterisk is displayed in the command window.
There have been quite a few implementaions and variations of Traceroute in recent years. Here are a few that stand out:
– TCPTraceRoute uses TCP Packets for hop count analysis and tracing.
– PathPing uses both Ping utility and Traceroute Functionality for analysis
– MTR, one of the more popular choices for Network Connectivity troubleshooting, also combines Traceroute and ping to troubleshoot hop by hop connectivity issues. MTR is available for both Unix/Linux and Windows Operating systems.
How to Use TraceRT
Using TraceRT is very simple – its as Easy as opening up a command line (cmd) and typing into the following command:
tracert <address you want to troubleshoot>
Here's an image of the Command line utility in action:
You can see that the packets travel through 2 different routers (22.214.171.124 and 126.96.36.199) before it reaches its destination address (188.8.131.52), which was specified in the original command. The first hop will usually be your Default Gateway within your network (or router).