What Is Traceroute?

Date First Published: 6th June 2022

Topic: Computer Networking

Subtopic: Network Software

Article Type: Computer Terms & Definitions

Difficulty: Medium

Difficulty Level: 6/10

CONTENTS

How Does Traceroute Work?

Learn more about what traceroute is in this article.

Traceroute, also known as tracert, is a command-line utility used to display the path the data packet took from its source to destination, also recording the duration of time that every hop makes along the way and the time that it took for each connection to take place. In order to provide a more accurate response time, each hop is queried multiple times, usually three. This command can be run by typing tracert [domain name (IP address or domain name name can be entered here)] in a command line. Traceroute was introduced by Van Jacobson in 1987.

Note:

In IPv6, the traceroute command has the name traceroute6 or tracert6.

Traceroute is helpful for determining the reason why a connection cannot be made or is taking too long to respond, since this command traces the path of connections from source to destination, which can show the location of the issues. Another command-line utility, called ping, is often used before traceroute to determine whether the host is reachable.

How Does Traceroute Work?

After the traceroute command is entered, the command-line utility sends an ICMP data packet with time-to-live (TTL) fields in the IP header. Each router that is involved in transferring data receives these packets. The ICMP packets give information about whether the routers can transfer the data in an effective way.

Every hop that handles the data packet takes away ‘1’ from the TTL of the packet. If the TTL reaches 0, the data packet has expired and gets discarded. The use of small TTL values that quickly expire forces routers to send these ICMP messages, which also identify the router.

At first, traceroute will display the IP address of the destination and the maximum number of hops before the trace is quit. Afterwards, it will display the name, IP address, and response time taken at every hop. If a hop fails to respond, an asterisk (*) is displayed and another hop is then tried.