OpenFlow is catalyzing the deployment of software defined networking (SDN) technologies around the globe. In practice, however, compatibility issues hinder the deployment of an OpenFlow control plane on a number of network platforms. The FP7 ALIEN project addresses this problem by introducing a Hardware Abstraction Layer (HAL) which enables OpenFlow capabilities on legacy network elements. This paper presents the implementation of a HAL on programmable network platforms with multi-core CPUs and summarizes the implementation experience gained in the process.