Quiz Entry - updated: 2026.07.14
What are the results when different DTP (Dynamic Trunking Protocol) modes are combined on each end of a link?
The outcome depends on both sides: two auto ports stay as access, but any combination involving trunk or desirable on at least one side forms a trunk. Two access ports or access + trunk cause limited connectivity.
| Dynamic Auto | Dynamic Desirable | Trunk | Access | |
|---|---|---|---|---|
| Dynamic Auto | Access | Trunk | Trunk | Access |
| Dynamic Desirable | Trunk | Trunk | Trunk | Access |
| Trunk | Trunk | Trunk | Trunk | Limited connectivity |
| Access | Access | Access | Limited connectivity | Access |
Key takeaways:
- Auto + Auto = Access — neither side actively initiates, so trunking never forms. This is the most common surprise
- Desirable + anything except access = Trunk — desirable actively tries to negotiate
- Trunk + Access = Limited connectivity — this is a misconfiguration. The trunk side tags frames that the access side doesn't understand
- Access + Access = Access — both are permanent access, works fine
The trick: Remember that dynamic auto is passive — two passive ends will never form a trunk. At least one side must be trunk or dynamic desirable to initiate trunking.
Tip: To avoid all this complexity, just set every port explicitly to access or trunk and disable DTP with nonegotiate.