The role of the interface in the VSAN. The value specifications
are listed as follows:
nonPrincipal - The state of the interface is not principal
interface in the VSAN.
principalUpstream - The state of the interface is upstream
principal interface in the VSAN.
principalDownstream - The state of the interface is downstream
principal interface in the VSAN.
isolated - The state of the interface is isolated in
the VSAN.
unknown - The state of the interface is unknown in
the VSAN.