Trunking - Computer Networks - VLANs

VLANs

In the context of Ethernet VLANs, Avaya and Cisco use the term Ethernet trunking to mean carrying multiple VLANs through a single network link through the use of a trunking protocol. To allow for multiple VLANs on one link, frames from individual VLANs must be identified. The most common and preferred method, IEEE 802.1Q adds a tag to the Ethernet frame, labeling it as belonging to a certain VLAN. Since 802.1Q is an open standard, it is the only option in an environment with multiple-vendor equipment. Cisco also has a proprietary trunking protocol called Inter-Switch Link which encapsulates the Ethernet frame with its own container, which labels the frame as belonging to a specific VLAN.