2Hierarchical Network Design The design of larger LANs includes identifying the following:An access layer that connects end users into the LANA distribution layer that provides policy-based connectivity between end-user LANsA core layer that provides the fastest connection between the distribution points
4FunctionalityThe network must work. The network must allow users to meet their job requirements. The network must provide user-to-user and user-to-application connectivity with reasonable speed and reliability.
5ScalabilityThe network must be able to grow. The initial design should grow without any major changes to the overall design.
6AdaptabilityThe network must be designed with a vision toward future technologies. The network should include no element that would limit implementation of new technologies as they become available.
7ManageabilityThe network should be designed to facilitate network monitoring and management to ensure ongoing stability of operation.
8LAN design considerations The function and placement of serversCollision detection issuesSegmentation issuesBroadcast domain issues
9Server Placement Enterprise servers Workgroup servers support all the usersshould be placed in the main distribution facility (MDF).Workgroup serverssupport a specific set of usersshould be placed in the intermediate distribution facility (IDF).
10Segmentationthe process of splitting a single collision domain into smaller collision domainsreduces the number of collisionsallows for greater utilization of bandwidthUsing Layer 2 devices such as bridges and switchesRouters reduce the size of the collision domain and the size of the broadcast domain at Layer 3
11LAN design methodology Gather requirements and expectationsAnalyze requirements and dataDesign the Layer 1, 2, and 3 LAN structure, or topology Document the logical and physical network implementation
12Availability measures Availability measures the usefulness of the network.things that affect availability:ThroughputResponse timeAccess to resourcesEvery customer has a different definition of availability.
13Design LAN StructureThe most common LAN topologies are star and extended starThe topology structure can be broken into OSI layers to determine devices to use
22Layer 1 DesignOne of the most important components to consider when designing a network is the physical cabling.
23Layer 1 Design Issue: Type of Cabling copper or fiber-optic?the overall structure of the cabling
24Some rules on CablingFiber-optic cable should be used in the backbone and risers in all cable designs.Category 5e UTP cable should be used in the horizontal runs.The cable upgrade should take priority over any other necessary changes.Enterprises should also make certain that these systems conform to well-defined industry standards, such as the TIA/EIA-568-A specifications.
26Typical MDF in Star Topology In a simple star topology with only one wiring closet, the MDF includes one or more horizontal cross-connect (HCC) patch panels.HCC patch cables are used to connect the Layer 1 horizontal cabling with the Layer 2 LAN switch ports.The uplink port of the LAN switch, depending on the model, is connected to the Ethernet port of the Layer 3 router using a patch cable. At this point, the end host has a complete physical connection to the router port.
27Multi-Building Campus When hosts in larger networks exceed the 100-meter limitation for Cat. 5e UTP, more than one wiring closet is required.Multiple wiring closets mean multiple catchment areas.The secondary wiring closets are referred to as IDFs.
28Extended-Star Topology in a Multi-Building Campus VCC is used to interconnect the various IDFs to the central MDF.IDFs should be connected to the MDF by vertical cabling, also called backbone cabling.Fiber-optic cable is normally used because the vertical cable lengths are typically longer than 100 meters
29Logical Diagramthe locations and identification of the MDF and IDF wiring closetsthe network topology model without all the details of the exact installation paths of the cablesthe basic road map of the LANthe number of spare cablesthe type and quantity of cables used to interconnect the IDFs with the MDF
30detailed documentation of all cable runs, the identification numbers, and the port the run is terminated on at the HCC or VCC.
31Devices at Layer 2 determine the size of the collision domains. Layer 2 DesignDevices at Layer 2 determine the size of the collision domains.
32Asymmetric Switchingprovides more bandwidth to vertical cabling, uplinks, and servers
33The desired capacity of a vertical cable run is greater than that of a horizontal cable run.
34Determine the number of 10 Mbps and 100 Mbps ports review of the user requirements for the number of horizontal cable drops per room and the number of total drops in any catchment area.This includes the number of vertical cable runs.E.g.: four horizontal cable runs per room; total 18 rooms; require 72 LAN switch ports
39Layer 3 Router for Segmentation All data traffic from Network 1 destined for Network 2 has to go through the router.There are two broadcast domains
40Logical Addressing Mapped to the Physical Network A standard convention should be set for addresses of important hosts on the network.
41Address Map and Logical Network Map provides a snapshot of the network
42helps to troubleshoot the network Physical Network Maphelps to troubleshoot the network
43VLAN Environmentcombines Layer 2 switching and Layer 3 routing technologieslimits both collision domains and broadcast domainsprovides security with the creation of VLAN groups
44Hierarchical LAN Design easier to make changes to the network as the organization grows
45Access layer switchesthe entry point for user workstations and servers to the networkprovides services such as VLAN membership.Access layer functions also include MAC layer filtering and microsegmentation
46Distribution layer Networks are segmented into broadcast domains Policies are applied and ACLs can filter packets.Switches in this layer operate at Layer 2 and Layer 3Distribution layer functions:Aggregation of the wiring closet connectionsBroadcast/multicast domain definitionVirtual LAN (VLAN) routingAny media transitions that need to occurSecurity
47Distribution layerThe following Cisco switches are suitable for the distribution layer: Catalyst 2926GCatalyst 5000 familyCatalyst 6000 family
48Core layer The core layer is a high-speed switching backbone. If the switch does not have a router module, an external router is used for the Layer 3 function.This layer should not perform any packet manipulation.A core infrastructure with redundant alternate paths gives stability to the networkAsynchronous Transfer Mode (ATM) or Ethernet switches can be used.
49Core layerThe following Cisco switches are suitable for the core layer:Catalyst 6500 seriesCatalyst 8500 seriesIGX 8400 seriesLightstream 1010