Cisco has defined a hierarchical model known as the
hierarchical
internetworking model. This model simplifies the task of building a reliable, scalable, and less expensive hierarchical internetwork because rather than focusing on packet construction, it focuses on the three functional areas, or layers, of your network:
Core layer: This layer is considered the backbone
of the network and includes the high-end switches
and high-speed cables such as fiber cables. This
layer of the network does not route traffic at the
LAN. In addition, no packet manipulation is done
by devices in this layer. Rather, this layer is concerned
with speed and ensures reliable delivery of packets.
Distribution layer: This layer includes LAN-based
routers and layer 3 switches. This layer ensures
that packets are properly routed between subnets
and VLANs in your enterprise. This layer is also
called the Workgroup layer.
Access layer: This layer includes hubs and switches.
This layer is also called the desktop layer because
it focuses on connecting client nodes, such as workstations
to the network. This layer ensures that packets are
delivered to end user computers.
Figure INT.2.1 displays the three layers of the Cisco hierarchical model.
When you implement these layers, each layer might comprise more than two devices or a single device might function across multiple layers.The benefits of the Cisco hierarchical model include:
