1. A method of configuring a virtual private network (VPN) within a shared network, comprising: creating a queue of configuration tasks for gateway devices belonging to the VPN, said configuration tasks including sending static network routing information to said gateway devices; and repeatedly retrieving a next task from the queue, wherein the retrieving further comprises: interrogating the gateway device to which the task relates, to identify any change in subnetworks connected thereto since the task was created; if no change is identified, performing the retrieved task; otherwise, if a change is identified, creating update configuration tasks for all relevant gateway devices in the VPN; merging the update task for each gateway device with any not yet performed task for that gateway device; and performing the task retrieved from the queue merged with the update task.