What could happen if the subnet mask is not correctly set between two devices?

• A. They could communicate freely
• B. They will be placed on different networks
• C. They will automatically find each other
• D. They will create a loop

Answer: (B)

When the subnet mask is not correctly set between two devices, the result is that they will be placed on different networks. The subnet mask defines the network portion and the host portion of an IP address. If the subnet masks of the two devices do not match or are configured incorrectly, the devices will mistakenly believe they are on different networks. This will prevent them from communicating directly with each other, as they will send data packets to the default gateway instead of directly to the other device.

For instance, if one device is set with a subnet mask of 255.255.255.0 and another device is set with 255.255.0.0, they may interpret their IP addresses as belonging to different networks due to the way the subnet mask divides the address. As a result, without correct configuration of the subnet masks, direct communication will fail.