What is a primary disadvantage of using TTL Scoping?

Using TTL (Time to Live) scoping is a technique employed in multicast routing to manage the reach of multicast packets within the network. The correct answer identifies a primary disadvantage whereby applications must support custom TTL values to function effectively with TTL scoping.

Custom TTL values are employed to determine how far multicast packets can travel through the network. If the applications do not have the capability to set or recognize these custom TTL values, it limits their ability to utilize multicast efficiently. This means that network engineers need to ensure that all relevant applications within the multicast path can handle these adjustments; otherwise, the packets may not reach their intended recipients, leading to suboptimal performance or complete packet loss.

In contrast, other options highlight different characteristics or limitations associated with multicast routing. While some could pertain to architectural choices or specific scenarios within multicast protocols, the need for application support for custom TTL values directly addresses a fundamental operational challenge that can undermine the utility of TTL scoping across an enterprise network.