What does the 802.1Q standard define?

The 802.1Q standard specifically defines VLAN (Virtual Local Area Network) tagging, which is crucial for managing and isolating traffic in network environments. VLAN tagging allows network switches to identify and separate different VLANs on a single physical network infrastructure. This is achieved by appending a tag to the Ethernet frame, which includes information about the VLAN to which the frame belongs.

This capability enhances network efficiency and security by allowing multiple virtual networks to coexist on the same physical hardware while maintaining distinct broadcast domains. Consequently, devices in different VLANs cannot communicate directly without a router or Layer 3 switch, which adds a layer of security and control over network traffic.

Understanding the function and implementation of 802.1Q is essential for anyone working with network configurations, particularly in environments that utilize VLANs for scalability and security purposes.