What is the primary disadvantage of Distance Vector protocols?

Distance Vector protocols primarily face the disadvantage of being susceptible to routing loops. This susceptibility arises from the way Distance Vector protocols function; they rely on each router sharing its known network distances with its immediate neighbors. Because of this reliance on a limited view of the network topology, inconsistencies can develop, leading to routing loops. These loops occur when packets circulate in the network without reaching their destination, which can result in inefficient routing and increased network congestion.

To mitigate this issue, Distance Vector protocols implement various techniques, such as defined timers, split horizon, and route poisoning, to help prevent these loops. However, these methods don't eliminate the fundamental problem entirely, thus making this a significant disadvantage compared to other routing protocols like Link State, which maintain a complete view of the network and are less prone to such issues.

The other options present different characteristics that are not the primary disadvantage of Distance Vector protocols. While manual configuration of routes and bandwidth usage can be considerations in specific contexts, they do not directly relate to the inherent design issues that lead to routing loops.