Enterprise Campus Modules

This section introduces the Enterprise Campus functional area and describes the purpose of each module therein. It also discusses connections with other modules. An enterprise campus site is a large site that is often the corporate headquarters or a major office.

Regional offices, SOHOs, and mobile workers might have to connect to the central campus for data and information. As illustrated in Figure 2.2.3, the Enterprise Campus functional area includes the Campus Infrastructure module and, typically, a Server Farm module.

Figure: Enterprise Campus Functional Area

Campus Infrastructure Module

The Campus Infrastructure design consists of several buildings connected across a Campus Core. The Campus Infrastructure module connects devices within a campus to the Server Farm and Enterprise Edge modules. A single building in a Campus Infrastructure design contains a Building

Access layer and a Building Distribution layer. When more buildings are added to the Campus Infrastructure, a backbone or Campus Core layer is added between buildings. The Campus Infrastructure module includes three layers:

■ The Building Access layer

■ The Building Distribution layer

■ The Campus Core layer

Building Access Layer

The Building Access layer, located within a campus building, aggregates end users from different workgroups and provides uplinks to the Building Distribution layer. It contains end-user devices such as workstations, Cisco IP phones, and networked printers, connected to Layer 2 access switches; VLANs and STP might also be supported. The Building Access layer provides important services, such as broadcast suppression, protocol filtering, network access, IP multicast, and QoS.

For high availability, the access switches are dual-attached to the distribution layer switches. The Building Access layer might also provide Power over Ethernet (PoE) and auxiliary VLANs to support voice services.

Building Distribution Layer

The Building Distribution layer aggregates the wiring closets within a building and provides connectivity to the Campus Core layer. It provides aggregation of the access layer networks using multilayer switching. The Building Distribution layer performs routing, QoS, and access control.

Requests for data flow into the multilayer switches and onward into the Campus Core layer; responses follow the reverse path. Redundancy and load balancing with the Building Access and Campus Core layer are recommended. For example, in Figure 3-11, the Building Distribution layer has two equal-cost paths into the Campus Core layer, providing fast failure recovery because each distribution switch maintains two equal-cost paths in its routing table to every destination network. If one connection to the Campus Core layer fails, all routes immediately switch over to the remaining path.

Campus Core Layer

The Campus Core layer is the core layer of the Campus Infrastructure module. Within the Enterprise Campus functional area, this high-performance, switched backbone connects the buildings and various parts of the campus. Specifically, this layer interconnects the Building

Distribution layer with the Server Farm and the Enterprise Edge modules. The Campus Core layer of the Campus Infrastructure module provides redundant and fastconverging connectivity between buildings and with the Server Farm and Enterprise Edge modules. It routes and switches traffic as quickly as possible from one module to another. This module usually uses multilayer switches for high-throughput functions with added routing, QoS, and security features.

Enterprise Campus Guidelines

Follow these guidelines for creating the modules within an Enterprise Campus functional area:

Step 1 Select modules within the campus that act as buildings with access and distribution layers.

Step 2 Determine the locations and the number of access switches and their uplinks to distribution layer switches.

Step 3 Select the appropriate distribution layer switches, taking into account the number of access layer switches and end users. Use at least two distribution layer switches for redundancy.

Step 4 Consider two uplink connections from each access layer switch to the two distribution layer switches.

Step 5 Determine where servers are or will be located, and design the Server Farm module with at least two distribution layer switches that connect all servers for full redundancy. Include out-of-band network management connections to all critical devices in the campus network.

Step 6 Design the Campus Infrastructure module’s Campus Core layer using at least two switches and provide for the expected traffic volume between modules.

Step 7 Interconnect all modules of the Enterprise Campus with the Campus Infrastructure module’s Campus Core layer in a redundant manner.