Many people have seen the message logged to their switch about a mismatched native VLAN on a trunk, but how is it detected? There are two methods of detecting mismatched native VLAN on a trunk link: To demonstrate how this
Native VLAN – why you should change it
The native VLAN (assuming 802.1Q) is a VLAN that is sent untagged by default. The default for Cisco switches is that all ports are in VLAN 1 and if trunking is used VLAN 1 will be sent untagged. VLAN 1