DTP - how to disable

Dynamic Trunking Protocol or DTP is automatically enabled on all Cisco IOS switches. Even if a port is explicitly set to trunk, DTP is still enabled on such ports, and negotiation will take place if the dynamic keyword is used on the remote switch.

In order to completely disable the sending and receiving of DTP messages on the port of a switch, one of two things must be configured:

  1. A port must be explicitly configured as an access port.
  2. A trunk port must be configured using the switchport nonegotiate command.