CCNP BSCI Notes – Network Design


Full mesh formula: n(n-1)/2

Example: To create a mesh between 8 nodes, 8 * (8-1) / 2 = 28; 28 links are needed.

Design concepts

Legacy Hierarchical Design Model

          Core – fast L2-switched backbone

          Distribution – L3 switches

          Access – dense L2 switches

This failed to address issues such as redundancy, Internet and remote access, and locating services.

Switch block design was introduced to add redundancy; this included redundant core and distribution switches and links per switch block.

Enterprise Composite Network Model

This new model was developed to address modern design considerations.

         Enterprise campus

                 Campus backbone (previously the "core")

                 Building distribution (previously "distribution")

                 Building access (previously "access")


                 Server farm (for internal enterprise services)

         Enterprise edge


                 Internet connectivity

                 Remote access

                 WAN (internal links)

         Service provider edge



                 Frame relay, ATM, PPP for private connectivity

Intelligent Information Network (IIN)

         Phase 1: Integrated transport – the shift toward the ECN model

         Phase 2: Integrated services – service virtualization (disassociation of services from individual machines)

         Phase 3: Integrated applications – recognizing and combining high-layer traffic properties (for example, Network Access Control)

Services-Oriented Network Architecture (SONA)

SONA is the application of IIN ideas to enterprise networks.

         Network infrastructure (IIN phase 1)

         Interactive services (IIN phase 2)

         Application (IIN phase 3)

Routing protocols

         Distance vector – a router will only exchange routes with a directly connected neighbor

         Link-state – a router advertises a list of all its neighbors and its neighbors’ networks; routers run SPF to determine the best path

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