A virtual routing system includes a number of physical routers. One of the physical routers is the master with respect to a given source of traffic, and the others are backups. If the master router fails, then one of the backup routers becomes the master to provide substantially uninterrupted service through the virtual routing system. A virtual redundant routing protocol (VRRP) can be extended to support sub-second advertising of VRRP packets by a master router a backup router. In some cases, sub-second switching is supported, in which a backup router can become a new master router after less than a second of down time by the original master router. Such responsiveness in a virtual routing system is very useful for many applications, such as voice-over-packet applications in which down time of the routing system for more than one second is unacceptable.