With the rapid development of vehicle technology and wireless communication technology, a vehicular ad hoc network (VANET) has come into sight as a vehicular application of the well-known mobile ad hoc networks (MANETs). In this paper, we consider the performance issue of a large-scale VANET and extend the technology of Mobile IP used in a MANET into the VANET. In our considered hierarchical structured VANET, each roadside gateway deployed on the roadside is responsible for forming a small-scale local VANET by clustering a number of vehicles nearby. We apply the destination-sequenced distance-vector (DSDV) routing protocol and the Mobile IP to support intra- and intercommunications of local VANETs. Our studies focus on the feasibility of the proposed architecture and evaluate its network performance through an analysis of connectivity. Moreover, we investigate the influence of main network configuration parameters on performance measures such as the mobility of node, the network density, and the number of gateways and demonstrate that the architecture we proposed can achieve good performance with proper configuration parameters.