If a VLAN header is present, what follows it?

When a VLAN header is present in a frame, the next field that follows it is the Ethertype field. This is a critical component of the Ethernet frame structure since it indicates the protocol encapsulated within the payload of the frame, which helps the receiving device understand how to process the data contained in the frame.

The Ethertype field defines the specific protocol being used, such as IPv4, IPv6, or other higher-level protocols. In the context of VLANs, this signaling is essential for network devices to interpret the traffic effectively and apply the correct forwarding rules as specified by the VLAN configuration.

Understanding the structure of a frame, specifically in the case of VLAN tagging, highlights how protocols stack on top of one another and helps to clarify configuration and troubleshooting processes involved in network management. This knowledge is particularly crucial for IT professionals tasked with managing and optimizing network performance, ensuring that device communication aligns with established protocols.