Another cause of failure apart from the connection to the provider or to another network may lie with the local gateway. Severe effects can result from the failure of a central VPN gateway that is used, for example, to connect the networks of multiple remote locations with the central network at headquarters.
To ensure that the headquarters remains in contact, multiple VPN endpoints (generally identically configured VPN gateways operated in parallel) can be installed. Should line polling (with dead-peer detection, ICMP line polling) indicate a failure, then a variety of strategies (e.g. the random selection of one of the available gateways) can be used to enable communication to a different VPN end point. At the central headquarters, the new router and the local default gateway are propagated by dynamic routing (RIP V2).
To avoid the situation where the additional VPN gateways "remain unused", intelligent "load balancing" ensures that all of the devices share the load of incoming and outgoing connections also under normal operating conditions.
