2.1.d Implement and troubleshoot trunking

2.1.d [iii] Native VLAN

A frame in the VLAN-aware portion of the network that does not contain a VLAN tag is assumed to be flowing on the native (or default) VLAN. By default , the switch forwards untagged traffic in the native VLAN configured for the port. The native VLAN is VLAN 1 by default.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1628-1629).  . Kindle Edition.