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chap03 - Cisco Router Handbook Sackett $70.00 98-7 Backward...

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Cisco Router Handbook Sackett $70.00 0-07-058098-7 Backward Forward Chapter: 1 | 2 | 3 | 4 | 5 | 6 _________________________________________________________________ _________________________________________________________________ Chapter Three Cisco Router Network Design The hierarchical structure of the Cisco router network design model is based on the type of services provided at each layer. The notion of using layers creates a modular architecture enabling growth and flexibility for new technologies at each layer. The Cisco hierarchical design model consists of three layers. Figure 3.1 diagrams the Cisco hierarchical design model. The core layer provides the high-speed backbone for moving data between the other layers. This layer is geared towards the delivery of packets and not packet inspection or manipulation. The distribution layer provided policy-based networking between the core and access layer. The distribution layer provides boundaries to the network topology and provides several services. These services are: * Address or area aggregation * Departmental or workgroup access * Broadcast/multicast domain definition * Virtual LAN (VLAN) routing * Any media transitions that need to occur * Security The access layer is the edge of the network. Being on the edge the access layer is the entry point to the network for the end user community. Devices participating in the access layer may perform the following functions: * Shared bandwidth * Switched bandwidth * MAC layer filtering * Microsegmentation It is important to remember that the Cisco hierarchical design model addresses functional services of a network. The different layers described may be found in routers or switches. Each device may partake in the functions of more than one layer. Separation of functional layers is not mandatory however; maintaining a hierarchical design fosters a network optimized for performance and management. 1. The Network Infrastructure Life-Cycle Every corporation has a network infrastructure in place as the framework supporting the business processes. Just as applications and systems have life cycles so does a network infrastructure. This section highlights a network infrastructure life-cycle that may be used as a general guideline for designing and implementing Cisco based networks. 1. Executive Corporate Vision
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Corporate organizational restructuring through regional consolidation or through business group integration will certainly have an effect on the network infrastructure. Aligning the corporate vision with the business directives builds the foundation for the network infrastructure. 2. Gather Network Infrastructure Information This involves research and discovery of the current network WAN topology as well as corporate and branch office LAN topologies. A full understanding of end-to-end network configuration is required. Additionally, bandwidth allocations and usage costs must be determined to provide the complete picture.
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