Native VLAN

802.1Q has a feature called the native VLAN.

The native VLAN is VLAN 1 by default on all trunk ports, however this can be manually configured on each trunk port.

The switch does not add an 802.1Q tag to frames in the native VLAN.

When a switch receives an untagged frame on a trunk port, it assumed the frame belongs to the native VLAN.

It's very important that the native VLAN matches!