In which scenario can identical IP addresses be used on the same Ethernet network?

On an Ethernet network, every device must have a unique IP address to ensure proper communication and avoid conflicts. When two devices have the same IP address on the same network, it creates an address conflict, leading to issues such as packet loss, inability to access network services, and overall network dysfunction.

The scenario where identical IP addresses are presumed to be usable relates to network design patterns, such as guest networks or VPNs, but those configurations still require that devices on the same local network segment maintain unique addresses to avoid collisions. For instance, even in guest networks or while connected through a VPN, different layers of networking or virtual network segments would manage these addresses to prevent duplication at the local level.

Therefore, the answer emphasizes the fundamental principle that no two devices on a single Ethernet network can share the same IP address without causing significant communication issues. This principle is critical to maintain a well-functioning and orderly network environment.