HOW TO READ TRACEROUTE AND TROUBLESHOOT USING TRACEROUTE

Traceroute is a diagnostic utility present and can be run in all systems like windows, Unix and operating systems in switches, routers etc. Unlike ping which only tests the connectivity between endpoints and doesn't have an output of letting you know where the problem is once you received a destination unreachable message, traceroute provides a detailed output of the path it traverses. The output contains the public IP addresses the packet arrives in and the providers connection to upstream providers.

Traceroute is a very helpful tool in troubleshooting internet connection. Most administrators use this utility to check their internet connection to their ISP in case they are experiencing slow or intermittent internet connection. Traceroute provides a detailed output if the traceroute is complete and has reached its destination (example, www.google.com or a address of a remote server) , latency measurement, number of hops it takes before reaching the destination. Basically traceroute diagnose the health of your internet connection if it is still efficient. Usually traceroute is up to 30 hops maximum and at some point, traceroutes at the end may end up in destination unreacheable message before it reaches the destination because the network where the destination IP address has already been firewalled. But this is just ok as long as the trace is complete and has traversed the provider and you can connect to the destination.

Trace route determines if the latency is within the customer's LAN, the providers network or to their upstream ISP's. Traceroute also becomes the basis for ISP engineers if they need to reroute the destination to a different upstream if latency has been identified to be too high. They usually check for number of hops cause less number of hops means less travel and less latency means faster connection.

Below are a sample traceoute and how to read and troubleshoot them.

Here is how you read a traceroute



Here's a weird traceroute where the traceroute loops and never reaches its destination.




Here is a traceroute where the problem is in the customer's LAN



Here is a traceroute before being rerouted.



...After being rerouted.