Home / Networking Basics / DTP modes on Cisco Catalyst Switches

DTP modes on Cisco Catalyst Switches

Cisco recommends to set trunking as static. But here is the behaviour if we don’t set it to “switchport mode trunk”.
For Catalyst 2960 and Catalyst 3560, I found that the default DTP mode is “dynamic auto”.
Key behaviours:

  • Dynamic auto+ dynamic auto = access
  • dynamic auto+ access/trunk = access/trunk
  • Dynamic desirable + access = access
  • Dynamic desirable + else = trunk

Default DTP modes

Here are a couple of outputs that reveal the default DTP modes, on Catalyst 2960 and Catalyst 3560:

Default DTP mode on Catalyst 2960
Default DTP mode on a 3560

A combination of DTP modes

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

When I set DTP mode to “dynamic desirable” on SW1 and “access” on SW0, each port on both sides of the link will operate in static access mode:

 

 

 

 

 

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:

Summary
Article Name
DTP modes on Cisco Catalyst Switches
Author
Top Courses in IT & Software 300x250

One comment

  1. thanks for posting :)

Leave a Reply

Your email address will not be published. Required fields are marked *

*

Adsense black background: