Which statement is true about IP source routing options?

• A. Only the destination prefix must be known, not the routers.
• B. Strict routing allows you to designate some routers that must be traversed.
• C. Loose routing requires all routers along the path to be designated.
• D. Strict routing requires all routers along the path to be designated.

Answer: (D)

IP source routing options let the sender embed a list of routers in the IP header so the path can be steered rather than left to the network. There are two modes. In strict source routing, the packet must go through every router in the listed sequence, with no deviations. That means every hop along the path is predetermined and the router must be one of the designated addresses in the exact order. In loose source routing, you specify a set of routers that must be visited, but the packet can traverse other routers between those points, allowing for some flexibility in the actual path.

This makes the statement that is true: strict routing requires all routers along the path to be designated. The other options mix up the ideas—for example, strict routing is not about designating only some routers, and loose routing does not require all hops to be designated—so they don’t fit.