The network is becoming the development focus for the in-vehicle electronic system. Network buses are used to improve communication between ECUs and to reduce the wiring costs. In-vehicle network buses, such as CAN, LIN, FlexRay, have become the central technique for sharing sensor data among vehicle ECUs. Gateways are a critical factor in vehicle network design with applications requiring the use of several networking standards. There are lots of networking protocols to choose from - each with advantages and disadvantages. No one protocol satisfies the requirements of all automotive applications. There is a need to consolidate data from these networks using de-centralized processing. As such, a gateway is used as a central hub to interconnect and process data from a vehicle's embedded networks. A gateway is composed of several automotive networking interfaces such as CAN, LIN and FlexRay in addition to embedded micro-controllers and peripheral functions. Meanwhile, simulation has becoming an efficient development tool used in the modern automotive industry. This paper will suggest a simulation solution for designing in-vehicle network gateways.