The correct answer is 'Bridge' because the bridge network driver provides a private network internal to the host machine, allowing containers connected to the same bridge network to communicate with each other while isolating them from other containers not connected to the bridge. The default bridge network does not provide isolation between containers, which is why it is necessary to create a user-defined bridge network for this scenario. The 'Overlay' network driver is used for networking between multiple Docker hosts, which is not the requirement here. The 'Host' mode removes network isolation and uses the host's networking directly, which does not meet the requirement for network isolation. 'Host' mode also would not use NAT because the containers would share the network with the host. Therefore, the 'Host' network driver is not suitable for this scenario.