What are the characteristics of virtual switch and etherstub and what are their differences

Virtual Switch

provides connection between VNICs and the physical NIC upon which the VNICs are built. The physical interface provides the system with it's external network connection
the VNIC has the same datalink interface as a physical interface

Example

# dladm create-vnic -l e1000g0 vnic0

# dladm create-vnic -l e1000g0 vnic1

This creates a virtual switch between the vnic0/vnic1 and the physical interface e1000g0

Etherstub

Purely software and do NOT require a network interface as the basis for the virtual network
VNICs created on etherstub are independent of the physical NICs in the system.
Can be used private or isolated virtual networks

# dladm create-etherstub stub0

# dladm create-vnic -l stub0 vnic0

# dladm create-vnic-l stub0 vnic1

etherstub stub0 is purely software and has no connection to any physical interface. The vnics (vnic0/vnic1) are created over the ether stub and are on a private isolated network