Dynamic Trunking Protocol (DTP) is the Cisco-proprietary protocol that actively attempts to negotiate a trunk link between two switches. Below is the switchport modes (or DTP modes) for easy reference:
|Dynamic Auto||Creates the trunk based on the DTP request from the neighboring switch.|
|Dynamic Desirable||Communicates to the neighboring switch via DTP that the interface would like|
to become a trunk if the neighboring switch interface is able to become a trunk.
|Trunk||Automatically enables trunking regardless of the state of the neighboring switch|
and regardless of any DTP requests sent from the neighboring switch.
|Access||Trunking is not allowed on this port regardless of the state of the neighboring|
switch interface and regardless of any DTP requests sent from the neighboring
|Nonegotiate||Prevents the interface from generating DTP frames. This command can be|
used only when the interface switchport mode is access or trunk. You must
manually configure the neighboring interface as a trunk interface to establish a
Below figure shows the combination of different modes