What common outcome can be caused by substituting an invalid MAC address?

Substituting an invalid MAC address can lead to a loss of network connectivity because network devices use MAC addresses to identify and communicate with each other on a local area network (LAN). Each device on the network has a unique MAC address that allows it to send and receive data packets properly. If an invalid MAC address is used, the network may not recognize the device or may not be able to route traffic to and from it correctly. This disruption in identification can prevent the device from joining the network or communicating with other devices, ultimately causing it to lose connectivity.

For instance, a device with a MAC address that does not exist on the network or conflicts with another device's address could experience issues connecting to the network, leading to a complete inability to access network resources or the internet. This situation highlights the critical role that MAC addresses play in network infrastructure and communication.