VLANs The Ethernet frames that have to be forwarded may reside in different VLANs. This implies that all Ethernet frames contain a (802.1Q) VLAN ID. Communication between different VLANs is not allowed on the link layer. Only routers can make connections between different VLANs. VLANs create thus separated logical Ethernet segments within a single physical segment.
Ethernet QoS Ethernet frames