Advanced Networking Administrator Test Prep

Answer: D - An effective subnet mask to implement VLSM for a Class C network with a point-to-point serial link is 255.255.255.252.

Key Takeaway: Only 2 IP addresses are required for a single point-to-point link, one for the serial interface of the router at each end. Using 255.255.255.252 as the subnet mask is often used for these types of links, as no IP addresses are wasted.