Embodiments herein generally provide techniques for upgrading a virtual router (VR) comprising first and second physical routers used to route data between network devices. Before upgrade the first physical router, one or more ports of the router are disabled which causes data paths previously flowing through the first router to flow through the second router. After performing the upgrade, the first router is rebooted and uses a unique router ID to discover the network topology of an external network coupled to the VR. Once the network topology is identified, the first router activates a routing application (e.g., a BGP routing application) which enables the router to process control plane traffic received from the second router. Once routing information is gathered, the first router is able to assume the responsibility of forwarding data packets in the network, thereby freeing the second router to be upgraded.