Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.

During configuration of trunk port, you may see this error,

Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.

Solution for Error,

enter command

switchport trunk encapsulation dot1q
switchport mode trunk

How to get serial number of VMware ESXi host from vSphere Client?

1. Login to vSphere Client to access VMware  ESXi host,

2. You will see given below page,

3. Click on Configuration Tab, Then Processors , You will see Service Tag at the end. Which is serial number of Host Machine. It will look like this,