Native VLAN Tagging
The Native VLAN is the VLAN assigned to untagged traffic on a trunk port, typically used to carry control plane protocols or non-802.1Q-compliant traffic. By default, many switches configure VLAN 1 as the native VLAN, although this can be changed for security or design purposes.
Native VLAN tagging refers to the practice of tagging frames even on the native VLAN, contrary to the default behavior where such frames remain untagged. Enabling native VLAN tagging helps prevent misconfigurations, such as VLAN mismatches between switches, which can lead to traffic loss or unpredictable behavior. This feature is especially beneficial in environments with strict VLAN segregation and security requirements.
Native VLAN tagging is applied in various ways on Cisco devices Native VLAN Tagging Configuration on Cisco Switches depending upon the platform and the IOS version.
Links:
https://networklessons.com/switching/802-1q-native-vlan-cisco-ios-switch