A DR site is maintained containing multiple VMs distributed across multiple hosts to which a multi-tiered application can be failed over from a production site. A network bubble is created in which the multi-tiered application can be fire drill tested without conflicting with the production instance. Each VM is cloned, and cloned VMs communicate using private IP addresses. A virtual switch is created on each host, and configured for cloned VM communication. On each host, a virtual router is configured with both a public virtual adapter and a private virtual adapter. The source VMs communicate using public IP addresses over the physical channel, via the external virtual switches on the hosts, and are available for failover from the production site. The cloned VMs communicate using private IP addresses via the virtual switches and private virtual adapters of the virtual routers, thereby forming the network bubble.