While working on VPCs I have encountered this awesome tool in AWS console, called reachability analyzer. As the name suggests this tool is used to analyze the connectivity between two endpoints , aws provides a very good list of options to choose an endpoints, see below…
This can be a very useful tool while troubleshooting. Lets see how we can configure it.
We can find this tool under monitoring and troubleshooting, click on create and analyze path option at the right side of the screen.
This will bring you to the next page to select source and destinations for which you would like to analyze the path.
In this page, we have a very crisp options to chose from, source, destination and protocol.
However, if you like to be granular, we have additional packet header level options too.
Once you put your source and destination and click on create path. It will create the analyzer and run it for you.It will also refresh the page to the one where analysis can be seen. Note down, for me it has provided the explanation that both the instances are sitting in different VPCs and VPCs are not connected. Hence my connectivity is not working. So, here I will put a transit gateway in between and check if results improve.
Now, the transit gateways are configured and you can see how the result has changed.
More importantly, if you scroll down this page you will find the full path that the packet has taken, and this information is the most awesome feature of this tool.
We have to pay $0.10 per connectivity analysis.