Which command is used to configure a switchport to dynamic desirable mode?

The command used to configure a switchport to dynamic desirable mode is 'switchport mode dynamic desirable.' This command enables the interface to actively negotiate trunking with a neighboring switch port. When a switchport is set to dynamic desirable mode, it can initiate the Dynamic Trunking Protocol (DTP) process to establish a trunk connection.

In this mode, the switchport will send DTP advertisements to neighboring devices, indicating that it is willing to form a trunk. If the neighboring port is set to trunk or dynamic auto mode, a trunk link will be formed. This setting is essential for scenarios in which trunk links need to be dynamically established without requiring manual configuration.

Other options, such as 'switchport mode dynamic auto,' would only allow the port to respond to DTP negotiations initiated by other ports rather than initiate them itself. The 'switchport mode trunk' command sets the interface as a trunk outright, which does not involve negotiation, and the 'switchport mode access' command configures the port for access mode, which is used for connecting end devices to the network. Thus, the 'switchport mode dynamic desirable' is specifically designed for dynamic trunk negotiation, making it the correct command for this scenario.