The original Route Distinguisher (RD) of a VPN route. For VPN routes
which are originated in a VRF or which are received from a CE the
original RD is equal to the RD of the VRF. For VPN routes which are
received from another PE and imported into a VRF, the original RD is the
RD which was received from the other PE (the RD of the route itself is
changed to the RD for the VRF when the route is imported into the VRF).
For non-VPN routes the value of this object is undefined.