As the volume of data keeps growing rapidly, more and more servers are continuously added into data centers. The industry experience indicates that, in order to reduce the cost and energy consumption, data enter network (DCN) can be expanded by adding a small number of servers from time to time instead of adding a huge number of servers at a time. The DCN structures with incremental scalability can be expanded gradually while their topological properites are preserved. In order to improve the performance of the DCN, dual-centric DCN structures are proposed. However, the incremental scalabilities of the current dual-centric DCNs are not good. This paper proposes a new type of dual-centric data center network structure called GHDC (Generalized Hypercube Data Center network architecture), which is constructed by using commodity switches and multi-port servers. After analyzing the shortest distance between any two vertices, a routing algorithm is developed. To achieve incremental scalability, two incomplete GHDC structures are proposed. A small number of servers can be added into the incomplete GHDC structures while their topological properties are maintained. The analysis results show that GHDC significantly outperform FCell, FRectangle and FSquare in terms of the incremental scalability and robustness. The average through-put of GHDC is approximately equal to that of FSquare and highter than that of FCell and FRectangle by about 17.45% and 25.5%. Compared with the FCell, FRectangle and FSquare, GHDC reduces the cost andenergy consumption by about 10.84%, 22.85% and 29.55%, respectively.