Explanation/Reference:
Section: Enterprise Network Design Explanation
Explanation:
The access layer typically performs Open Systems Interconnection (OSI) Layer 2 switching and Network Admission Control (NAC) for end users. The access layer is the network hierarchical layer where end-user devices connect to the network. Port security and Spanning Tree Protocol (STP) toolkit features like PortFast are typically implemented in the access layer.
The distribution layer of a hierarchical design, not the access layer, provides address summarization, aggregates LAN wiring closets, and aggregates WAN connections. The distribution layer is used to connect the devices at the access layer to those in the core layer. Therefore, the distribution layer isolates the access layer from the core layer. In addition to these features, the distribution layer can also be used to provide policy-based routing, security filtering, redundancy, load balancing, Quality of Service (QoS), virtual LAN (VLAN) segregation of departments, inter-VLAN routing, translation between types of network media, routing protocol redistribution, and more.
The core layer of a hierarchical design, not the access layer, is also known as the backbone layer. The core layer is used to provide connectivity to devices connected through the distribution layer. In addition, it is the layer that is typically connected to enterprise edge modules. Cisco recommends that the core layer provide fast transport, high reliability, redundancy, fault tolerance, low latency, limited diameter, and QoS.
However, the core layer should not include features that could inhibit CPU performance. For example, packet manipulation that results from some security, QoS, classification, or inspection features can be a drain on resources.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 2, Access Layer, pp. 44-46
Cisco: High Availability Campus Network DesignRouted Access Layer using EIGRP or OSPF: Hierarchical Design