350-401 Practice Question: Given the following configuration on a Cisco IOS…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  The interface will actively try to form a trunk and will succeed if the other side is set to trunk, desirable, or auto.

  Why this is correct

  Dynamic desirable mode actively transmits DTP frames to initiate trunk negotiation, and it will successfully establish a trunk when the neighbor is configured as trunk (unconditional), desirable (actively negotiates), or auto (passively accepts). Only a neighbor explicitly set to access mode will refuse the DTP messages, leaving the link in access state. Therefore, the interface always attempts to trunk, and the outcome depends entirely on the peer's willingness to participate in negotiation.

• ✗

  The interface will only become a trunk if the other side is set to trunk.

  Why it's wrong here

  This statement is incorrect because it severely narrows the set of compatible peer modes. A dynamic desirable interface can also form a trunk with a neighbor in desirable mode, where both sides actively send DTP frames and rapidly agree, or with a neighbor in auto mode, where the desirable side initiates and the auto side simply responds affirmatively. The only mode that prevents a trunk is access, which ignores DTP packets, so limiting success to only the 'trunk' setting ignores two other common and valid configurations.

• ✗

  The interface will always remain an access port.

  Why it's wrong here

  This is false because dynamic desirable does not statically bind the interface to access mode; instead, it places the port in a negotiation state where it actively seeks to become a trunk. The port will remain an access port only when the far end is also configured as access, causing both sides to overlook DTP messages, or when DTP frames are disabled or dropped due to misconfiguration. Since the default behavior of desirable is to try for a trunk, saying it 'always' stays access contradicts the purpose of the mode and the negotiation outcomes possible.

• ✗

  The interface will not send DTP frames.

  Why it's wrong here

  This is incorrect because dynamic desirable is specifically the DTP mode that actively generates and sends DTP frames to invite the neighbor into trunk negotiation. Unlike dynamic auto, which listens passively and sends DTP packets only in response to received ones, dynamic desirable sends DTP frames immediately upon link up and continues to send them periodically. This proactive sending is exactly how a desirable port can convert an auto port into a trunk, so the claim that it would not send DTP frames confuses it with the more passive dynamic auto mode.

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