The previous sections discussed interfaces that belong to only one VLAN. These are sometimes referred to as access links and are completely transparent to the users. The users have no knowledge of the existence of the VLAN. However, to maintain VLAN information, the originating frame from a user must contain VLAN information that the switch fabric can use to forward the frame.
As a frame enters the switch fabric, it's encapsulated or tagged with some additional information that identifies VLAN properties for the frame as it is switched through the switch fabric. This includes the VLAN ID or number, sometimes referred to as the VLAN color. This additional information remains on the frame as it's forwarded across the switched ...