Final answer:
SR-IOV cannot be enabled after a virtual switch has been created; it is a hardware-based technology that has to be configured on the host and the virtual switch before it can be used by VMs, unlike software-based options VMQ, VMMQ, and vRSS.
Step-by-step explanation:
The technology among the options provided that cannot be enabled after the virtual switch has been created is SR-IOV (Single Root I/O Virtualization). SR-IOV is a hardware-based technology that allows a single physical PCI Express (PCIe) device to be shared among multiple virtual machines (VMs) with the goal of improving network performance. Enabling SR-IOV requires support in the physical network adapter and must be configured on the host and the virtual switch before VMs can utilize it. Unlike VMQ, VMMQ, and vRSS, which are software features and can be configured at any time, SR-IOV must be enabled on the physical adapter before the creation of the virtual switch.