Which interface command makes the switch actively attempt to form a trunk with a neighbor using DTP?

The switchport mode dynamic desirable command configures the switch port to actively attempt to convert the link into a trunk link. It sends DTP (Dynamic Trunking Protocol) frames to the neighboring switch, proposing to form a trunk. switchport mode trunk forces the interface into permanent trunking mode and generates DTP messages, but it doesn't actively negotiate; it assumes the other side will also trunk or be configured as desirable/auto. switchport nonegotiate disables DTP on the interface, preventing it from forming a trunk dynamically. switchport mode dynamic auto makes the interface willing to form a trunk if the neighboring interface is configured as desirable or trunk, but it does not actively initiate the trunking process itself.