What setting ensures that virtual networks on a virtual switch are isolated from each other?

The setting that ensures virtual networks on a virtual switch are isolated from each other is the VLAN ID. A VLAN (Virtual Local Area Network) allows network administrators to create separate broadcast domains within a virtualized environment. Each VLAN is assigned a unique VLAN ID, which is used by the virtual switch to segregate traffic among different VLANs.

When multiple virtual machines (VMs) are connected to the same virtual switch but assigned different VLAN IDs, the switch will keep their network traffic separate. This means that a VM with one VLAN ID cannot communicate directly with a VM assigned a different VLAN ID without proper routing in place, ensuring security and reducing unnecessary broadcast traffic across the network.

The other choices, while related to network management, do not serve the same purpose of isolating virtual networks. Port ID refers to specific ports on the switch, Network Label generally denotes a name or identifier for a network rather than an isolation mechanism, and Security Policy pertains to setting rules and configurations for security but does not directly influence the isolation of network traffic.