Recent growth of optical networks requires the installation of new and upgrade of existing components to support increased capacity demands. The task of designing optical transport systems and selecting equipment requires taking into account installed equipment as well as transceivers and (R)OADMs available at a moment. Often real OADMs, MDXs and transceivers operate at particular wavelengths, i.e. equipment is wavelength specific. Eventually, when designing a network, an engineer should take into account topology constraints such as optical channel path budget and equipment operating parameters such as transceiver reach and sensitivity. As WDM optical communication systems evolve from simple point-to-point links to complex network architectures, the optimized design of add/drop equipment and effective wavelength utilization becomes a challenging task when considering equipment constraints. We demonstrate an algorithmic approach, that offers an efficient method for the wavelength assignment and add/drop equipment allocation problem. This approach, which could be part of a comprehensive planning environment, allows optical network engineers to design cost effective add/drop equipment configurations with the most compact wavelength plan, resulting in the effective utilization of the DWDM grid. Our approach accounts for future channel loading, optical channel path parameters, e.g. its length, traffic demand parameters such as signal rate, equipment parameters such as add/drop port capability, operating wavelengths, transceiver bandwidth, etc. We will demonstrate how this approach will provide an easy way to design an optical network from scratch or upgrade the configuration of the existing ones. Different node architectures, including WSS based configurations or cascaded OADMs can be accommodated.