Full form: Dynamic Trunking Protocol
Also known as: Dynamic Trunking Protocol
Quick Definition
A Cisco proprietary protocol that automatically negotiates trunk formation between switches.
DTP is a Cisco proprietary protocol that allows switches to negotiate whether to form a trunk link. DTP modes include: Dynamic Auto (waits for the other side to initiate), Dynamic Desirable (actively tries to form a trunk), Trunk (forces trunk mode), and Access (forces access mode). The combination of modes on each end determines whether a trunk forms. DTP is enabled by default on most Cisco switch ports.
switchport mode dynamic desirable ! actively negotiates trunk switchport mode dynamic auto ! passively waits switchport nonegotiate ! disables DTP
Best practice is to disable DTP on access ports ('switchport mode access') and on trunk ports ('switchport nonegotiate'). Leaving DTP enabled allows an attacker to negotiate a trunk and send tagged frames — a VLAN hopping attack.
DTP is a Cisco proprietary protocol that allows switches to negotiate whether to form a trunk link. DTP modes include: Dynamic Auto (waits for the other side to initiate), Dynamic Desirable (actively tries to form a trunk), Trunk (forces trunk mode), and Access (forces access mode). The combination of modes on each end determines whether a trunk forms. DTP is enabled by default on most Cisco switch ports.
Best practice is to disable DTP on access ports ('switchport mode access') and on trunk ports ('switchport nonegotiate'). Leaving DTP enabled allows an attacker to negotiate a trunk and send tagged frames — a VLAN hopping attack.
DTP falls under the VLANs domain of the 200-301 exam. Understanding it in context with related terms like vlan and trunk-port is essential for answering scenario-based questions correctly.