In this short port we explore the possible DTP modes and configure them on a Catalyst switch. We also learn what the outcome would be if we combine them.
For Catalyst 2960 and Catalyst 3560, I found that the default Dynamic Trunking Protocol mode is “dynamic auto”.
- Dynamic auto+ dynamic auto = access
- dynamic auto+ access/trunk = access/trunk
- Dynamic desirable + access = access
- Dynamic desirable + else = trunk
Here are a couple of outputs that reveal the default Dynamic Trunking Protocol modes, on Catalyst 2960 and Catalyst 3560:
A combination of the above
I’m going to set different DTP modes on both ends of the link, and see the behaviour of DTP on Catalyst switches. I have SW1 and SW0.
Dynamic desirable + Access –> Access
Dynamic Desirable + else –> Trunk
When I set DTP mode to “dynamic desirable” on SW1 and leave the default value on SW0, the port on SW1 will operate in static access mode. However, the port on SW0 will operate as a trunk: