When using 802.1Q, which VLAN are DTP frames sent in?

When using 802.1Q, DTP (Dynamic Trunking Protocol) frames are sent in the native VLAN. In a standard configuration, the native VLAN is typically set to VLAN 1 by default, but it can be changed as needed. The reason DTP frames utilize the native VLAN is that these frames need to be able to traverse the trunk link without being tagged; this is crucial for establishing trunk links between devices.

In 802.1Q encapsulation, frames from VLANs other than the native VLAN are tagged with a VLAN ID, but frames from the native VLAN are sent untagged. Therefore, DTP frames must be sent in the native VLAN to ensure that they can be communicated properly without being interrupted by VLAN tagging. When DTP frames are transmitted, devices use this method to discover neighboring trunking capabilities and negotiate trunk links accordingly.