Cisco Certified Network Associate (CCNA) 2025 – 400 Free Practice Questions to Pass the Exam

The primary function of the Nonegotiate mode in Dynamic Trunking Protocol (DTP) is to prevent trunking on the port, regardless of DTP. When a switch port is set to Nonegotiate mode, it will not participate in the DTP negotiation process, which is used to automatically establish trunk links between switches. This means that even if the neighboring switch is configured to use DTP and attempts to negotiate trunking, the port in Nonegotiate mode will not respond or take part in that negotiation.

By using Nonegotiate mode, administrators can ensure that a certain port will remain in access mode or will not form a trunk connection, adding a layer of control over how switch ports interact with their neighbors. This is particularly useful in scenarios where you want to enforce specific configurations on the switch to avoid unwanted trunking configurations or to adhere to network policies.

In contrast, other modes such as "desirable" actively attempt to negotiate trunking, while "auto" responds to DTP frames from other devices, potentially allowing unwanted trunking if not carefully managed. Therefore, Nonegotiate mode provides a straightforward way to enforce access mode and ensure that a port does not become a trunk inadvertently.