In this paper we propose a dynamic multi-layer path computation algorithm which favors the re-usage of FA LSPs (Forwarding Adjacency Label Switched Path) and virtual links over a new LSP establishment. To evaluate the algorithm, we explore several approaches for the dynamic configuration of the Virtual Network Topology (VNT) within a multi-layer network (Connection - Oriented Ethernet transport over a Wavelength Switched Optical Network) controlled by a unified GMPLS control plane. Specifically, three VNT approaches are compared: the virtual approach, where some lambda FA LSPs are pre-computed but not established (i.e., virtual TE links), the semi-dynamic approach, where a specific set of lambda FA LSPs is pre-established and advertised as Ethernet TE links (i.e., FA TE links) and the dynamic approach, where there are neither pre-established nor pre-computed lambda FA LSPs.