Cisco IOS Embedded Event Manager (EEM)

Hello Chase

The confusion seems to come from the use of the word “simultaneously.” A better word to be used would probably be “synchronously”. I’ve made the change in the NetworkLessons note. In the context of EEM, the “sync yes” parameter does not mean that the EEM script and the CLI command will run at the exact same time.

What it actually means is that when a CLI command that triggers an EEM applet is entered, the EEM applet will start executing immediately without waiting for the CLI command to finish. However, the CLI command will not be executed until the EEM script has finished running. So, they are not running at the exact same time, but the EEM script starts running immediately when the CLI command is entered.

On the other hand, if you use “sync no”, the EEM script will not start running until the CLI command has finished executing.

This is why the lesson says “The ‘sync yes’ parameter is required. This tells EEM to run the script before running the show run command”. It’s a bit of a simplification, but it captures the essential point: with “sync yes”, the EEM script starts running immediately and the CLI command waits for it to finish.

Ultimately, I would suggest you experiment with the various options to see the behavior on a real or simulated device. It’s the best way to really understand deeply how these keywords affect the behavior of the EEM script and the related CLI commands.

I hope this has been helpful!