Cisco's hierarchical internetworking model consists of which three layers?

• A. Core, Edge, Access
• B. Backbone, Distribution, Access
• C. Core, Aggregation, Access
• D. Core, Distribution, Access

Answer: (D)

Cisco's hierarchical model organizes the network into three layers to keep functions separate and scalable: Access, Distribution, and Core. The three layers in practice are Core, Distribution, and Access. The Core provides the fast, high-capacity backbone that forwards traffic with minimal policy processing. The Distribution layer sits between the access devices and the core, aggregating traffic from multiple access switches and enforcing routing, security, and QoS policies. The Access layer is where end-user devices connect, handling VLANs, port security, and basic switching.

Because the question asks for the three layers of this model, the standard trio is Core, Distribution, and Access. Other labels like Edge, Backbone, or Aggregation don’t align with this canonical three-layer structure, so they aren’t the correct set.