Cisco Catalyst 6880-X Specifications download pdf (Page 12)

Introduction April 2014

Distribution Layer

The distribution layer supports many important services for the LAN. The primary function is to serve as an

aggregation point for multiple access layer switches in a given location or campus, and serve as the demarcation

between the layer-2 switching and layer-3 routing functions in this design. In a network where connectivity needs

to traverse the campus network end-to-end, whether between different access layer devices or from an access

layer device to the WAN, the distribution layer facilitates this connectivity.

Scalability

In any network where multiple access layer devices exist at a location to serve end-user connectivity, it becomes

impractical to completely interconnect all access switches as the access layer grows beyond two or three

switches.

The distribution layer provides a logical point to summarize addressing and to create a boundary for protocols

and features necessary for the access layer operation. Another benefit of the distribution layer boundary is that

it creates fault domains that serve to contain failures or network changes to those parts of the network directly

affected.

The end result to the organization is that the distribution layer can lower the cost of operating the network by

making it more efficient, by requiring less memory, and by processing resources for devices elsewhere in the

network. The distribution layer also increases network availability by containing failures to smaller domains.

Reduce Complexity and Increase Resiliency

This design uses a simplified distribution layer. Organizations benefit from the consistency and reduced

complexity features of the simplified distribution layer design by lower operational costs of configuring and

maintaining the network.

The simplified distribution layer design consists of a single logical entity that can be implemented using a pair of

physically separate switches operating as one device, or a physical stack of switches operating as one device.

Using a single logical entity reduces complexity of configuring and operating the distribution layer, as fewer

protocols are required and little or no tuning is needed to provide near-second or sub-second convergence

around failures or disruptions.

The design resiliency is provided using physically redundant components such as power supplies, supervisors,

and modules, as well as implementing Stateful Switchover with redundant logical control planes. There are other

variations not validated as part of this design, which may meet the needs of an organization with less stringent

redundancy requirements for their distribution layer. For example, a single physical device with redundant

components could be suitable for a high-density space-constrained environment.

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Cisco Catalyst 6880-X Specifications Page 12