What happens when one switchport is in dynamic desirable mode and the other is in dynamic auto?

When one switch port is configured in dynamic desirable mode and the other in dynamic auto mode, the two ports will negotiate to form a trunk link. In dynamic desirable mode, the switch actively attempts to create a trunk link by sending out Dynamic Trunking Protocol (DTP) messages to negotiate trunking. Meanwhile, the switch in dynamic auto mode is set to respond to DTP messages but does not actively initiate the negotiation itself.

In this scenario, the switch in dynamic desirable mode will successfully negotiate the trunking with the switch in dynamic auto mode, leading to the establishment of a trunk link. This allows for the transmission of multiple VLAN traffic across the link, unlike access ports, which handle a single VLAN. The ability to form a trunk link is essential in a switched network to ensure efficient use of network resources and bandwidth.