Answer: D
Explanation:
Disabling Dynamic Trunking Protocol (DTP)
Cisco’s Dynamic Trunking Protocol can facilitate the automatic creation of trunks between two switches. When two connected ports are configured in dynamic mode, and at least one of the ports is configured as desirable, the two switches will negotiate the formation of a trunk across the link. DTP isn’t to be confused with VLAN Trunking Protocol (VTP), although the VTP domain does come into play.
DTP on the wire is pretty simple, essentially only advertising the VTP domain, the status of the interface, and it’s DTP type. These packets are transmitted in the native (or access) VLAN every 60 seconds both natively and with ISL encapsulation (tagged as VLAN 1) when DTP is enabled.
The answer is A. STP and DTP use the native vlan to transmit data, while CDP, PAgP, VTP and UDLD use Vlan 1: https://learningnetwork.cisco.com/thread/85047
Correct answer are A & C
On an 802.1Q trunk, DTP packets are sent on the native VLAN. This is the case even if the native VLAN has been cleared from the trunk.
On an ISL trunk, DTP packets are sent on VLAN1. This is the case even if VLAN 1 has been cleared from the trunk and is no longer the native VLAN.
The correct answer could be both A and D. However A is maybe better because in CCNA used encapsulation is 802.1Q trunk. Still this is a pretty dirty question because it has 2 correct answers. Great question CISCO. Keep going.
The answer is C:
https://networklessons.com/switching/cisco-dtp-dynamic-trunking-protocol-negotiation
“By default DTP is enabled and the interfaces of your switches will be in “dynamic auto” or “dynamic desirable” mode.”
I couldn’t find any online article stating that DTP is using the native VLAN or VLAN 1.