Which network topology is least reliable and why?

The bus topology is considered the least reliable among the options provided because it operates on a single central cable (the bus) to which all network devices are connected. This means that if the main cable experiences a failure, it can disrupt the entire network. In essence, all devices are dependent on this one connection; if the cable is severed or a termination fails, communication between devices is halted. This makes troubleshooting more challenging as well, since isolating the problem may require an inspection of the entire network cable.

In a bus topology, there is no redundancy; therefore, any break in the cable leads to an inability for devices to communicate. This limitation underscores the inherent vulnerability of bus topology compared to other configurations like mesh or ring, which incorporate redundancy and alternative pathways for data transmission, enhancing overall reliability.