The Tag Protocol ID (ethertype) which for 802.1q trunking will always be 0x8100, the user priority which is 3 bits and this is used for Class of Service (802.1p) which is a QoS mechanism on trunk interfaces between switches, the CFI (Canonical Format Indicator) which is now used as the DEI (Drop. Inside a Layer 2 frame there is a four byte tag used for 802.1q, this tag is divided into 4 fields.GNS3 also has the capability to utilize containers. These appliances range from Cisco routers and switches to nodes such as Windows Server, CentOS, and Fedora. The software can virtualize or emulate a variety of systems called appliances.
