IEEE is the standard for VLAN tagging on Ethernet. It inserts a -byte tag into the Ethernet frame between the source MAC address and the EtherType field. This tag identifies which VLAN the frame belongs to. Before , Cisco used a proprietary protocol called ISL. Today, is universal. Every vendor supports it, making it the only tagging method you need to learn for modern networks.
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$ curl repovive.com/roadmaps/network-design/switching-and-vlans/802-1q-standard
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