The physical port to which this interface is bound. If vRtrIfPortID is
zero (0), then there is no binding between this virtual router
interface and a physical port. Once an interface has been bound to a
port, several steps are required to change the binding to some other
TmnxPortID value.
vRtrIfAdminState must be 'outOfService'; vRtrIfPortID must be set to
zero (0) to disassociate the interface from the original port binding;
finally, set vRtrIfPortID to the value for the new port binding.
Setting vRtrIfPortID to 0x20000001 indicates that this interface is the
system interface for the device.