Router virtualization seems as the obvious next step to system virtualization and the key to easily deploy and manage next generation overlay virtual networks. In this paper, we investigate the viability of virtual routers on a Xen-based system. We first evaluate the system throughput when achieving forwarding in the virtual routers. Then, we consider the context where virtual routers are dedicated to flows of different types and propose a mechanism to guarantee the required throughput and latency to real time applications while maintaining an optimal aggregated system throughput. We achieved this through both configuring the Xen Credit scheduler and establishing priorities between packets in the driver domain before switching them to the target virtual router.