© 1999, Cisco Systems, Inc. 1-1 Chapter 2 Overview of a Campus Network © 1999, Cisco Systems, Inc.

BCMSN—2-2 Discuss the forces that impact the design of campus networks Describe Layer 2, 3, 4, and Multilayer Switching functions Identify the hierarchical layer solution for a given network requirement Discuss the elements of the building block approach Identify the correct Cisco product solution, given a set of customer requirements Objectives Upon completion of this chapter, you will be able to perform the following tasks:

© 1999, Cisco Systems, Inc. BCMSN—2-3 In this chapter, we discuss the following topics: Campus network overview The emerging campus model The hierarchical model Campus Network Overview

© 1999, Cisco Systems, Inc. BCMSN—2-4 The following section discusses: Campus Network Overview Traditional Campus Networks Issues and Solutions Traffic Patterns The Emerging Campus Model The Hierarchical Model Campus Network Overview (cont.)

© 1999, Cisco Systems, Inc. BCMSN—2-5 Characteristics of a Campus Network Fixed geographic area Owned and administered by organization

© 1999, Cisco Systems, Inc. BCMSN—2-6 Traditional Campus Networks Collision Domain 1 Collision Domain 2 Broadcast Domain Bridges terminate collision domains

© 1999, Cisco Systems, Inc. BCMSN—2-7 Performance Issues Multicast, broadcast, and unknown destination events become global events Server A ARP I need to know the MAC address for Server A ARP

© 1999, Cisco Systems, Inc. BCMSN—2-8 Broadcast Issues Broadcasts can consume all available bandwidth Each device must decode the broadcast frame Server A

© 1999, Cisco Systems, Inc. BCMSN—2-9 Solution: Localizing Traffic LAN broadcasts terminate at the router interface

© 1999, Cisco Systems, Inc. BCMSN—2-10 Solution: Localizing Traffic (Cont.) VLAN3 VLAN2VLAN1 VLANs contain broadcast traffic and separate traffic flows

© 1999, Cisco Systems, Inc. BCMSN—2-11 VLAN7 VLAN6 VLAN5 Current Campus Networks VLAN3 VLAN2 VLAN1 VLAN10 VLAN9 VLAN8 Layer 3 devices interconnect LAN segments while still containing broadcast domains

© 1999, Cisco Systems, Inc. BCMSN—2-12 Understanding Traffic Patterns Successful network implementations consider traffic patterns

© 1999, Cisco Systems, Inc. BCMSN—2-13 The 80/20 Rule 80 percent of the traffic is local; 20 percent is remote VLAN3 VLAN2VLAN1 80+% Local Traffic 80+% Local Traffic 80+% Local Traffic 80+% Local Traffic 80+% Local Traffic 80+% Local Traffic 20% Remote Traffic

© 1999, Cisco Systems, Inc. BCMSN—2-14 The New 20/80 Rule 20 percent of the traffic is local; 80 percent is remote VLAN3 VLAN2VLAN1 20% Local Traffic 20% Local Traffic 20% Local Traffic 20% Local Traffic 20% Local Traffic 20% Local Traffic 80+% Remote Traffic

© 1999, Cisco Systems, Inc. BCMSN—2-15 VLAN4 Emerging Traffic Patterns The 20/80 rule challenges VLAN implementation VLAN3 VLAN2VLAN1

© 1999, Cisco Systems, Inc. BCMSN—2-16 Campus Network Overview The Emerging Campus Model –Customer requirements –Emerging campus structure –Switching technologies The Hierarchical Model Campus Network Overview This section discusses the following:

© 1999, Cisco Systems, Inc. BCMSN—2-17 Customer Network Requirements Fast convergence Deterministic paths Deterministic failover Scalable size and throughput Centralize applications The new 80/20 rule Multiprotocol support Multicasting

© 1999, Cisco Systems, Inc. BCMSN—2-18 Emerging Campus Structure Remote Services Enterprise Services Local Services Traffic patterns dictate the placement of services 80% Non- Local Traffic

© 1999, Cisco Systems, Inc. BCMSN—2-19 Local Services Devices connected by switches Traffic within the same subnet/VLAN Traffic does not cross the backbone

© 1999, Cisco Systems, Inc. BCMSN—2-20 Remote Services Devices connected by routers Traffic crosses subnet/VLAN Segregated by Layer 3 Traffic may/may not cross the backbone

© 1999, Cisco Systems, Inc. BCMSN—2-21 Enterprise Services Common to all users Traffic crosses subnet/VLAN Traffic crosses the backbone Segregated by Layer 3 May be grouped by Layer 2

© 1999, Cisco Systems, Inc. BCMSN—2-22 Basic Layer Terminology Transport Layer Data Link Network Layer Physical Session Presentation Application Segments Packets Frames Logical Ports Routers Switches/ Bridges

© 1999, Cisco Systems, Inc. BCMSN—2-23 Layer 2 Switching Data Link Hardware-based bridging Wire-speed performance High-speed scalability Low latency MAC address Low cost

© 1999, Cisco Systems, Inc. BCMSN—2-24 Impact of Layer 2 Switching Layer 2 switched networks have the same characteristics as bridged networks

© 1999, Cisco Systems, Inc. BCMSN—2-25 Benefits of Routing Broadcast control Multicast control Optimal path determination Traffic management Logical addressing Layer 3 security E E E0 E

© 1999, Cisco Systems, Inc. BCMSN— Layer 3 Switching Network Layer Hardware-based packet forwarding High-performance packet switching High-speed scalability Low latency Lower per-port cost Flow accounting Security QoS

© 1999, Cisco Systems, Inc. BCMSN—2-27 Layer 3 Switching (Text Only)

© 1999, Cisco Systems, Inc. BCMSN—2-28 Layer 4 Switching Transport Layer Based on Layer 3 Based on application- related information

© 1999, Cisco Systems, Inc. BCMSN—2-29 Multilayer Switching Transport Layer Data Link Network Layer Combines functionality of: –Layer 2 switching –Layer 3 switching –Layer 4 switching High-speed scalability Low latency

© 1999, Cisco Systems, Inc. BCMSN—2-30 Campus Network Overview The Emerging Campus Model The Hierarchical Model –Access, Distribution, and Core Layers –The building block approach –Campus network availability example Campus Network Overview The following section discusses:

© 1999, Cisco Systems, Inc. BCMSN—2-31 The Hierarchical Model Distribution Layer Core Layer Access Layer

© 1999, Cisco Systems, Inc. BCMSN—2-32 Access Layer Entry point to the network Shared bandwidth Layer 2 services –Filtering –VLAN membership Access Layer

© 1999, Cisco Systems, Inc. BCMSN—2-33 Distribution Layer Access aggregation point Workgroup services access Broadcast domains definition InterVLAN routing Media translation Security Distribution Layer

© 1999, Cisco Systems, Inc. BCMSN—2-34 The Core Layer Fast transport No Layer 3 processing Core Layer

© 1999, Cisco Systems, Inc. BCMSN—2-35 Distribution Layer Core Layer Access Layer Choosing a Cisco Product C4xxx C5xxxC29xx 35xx C19xx Catalyst 19xx/29xx/3500 < 50 ports Catalyst 4xxx < 100 ports Catalyst 5xxx >100 ports Catalyst 55xx Catalyst 6xxx Catalyst 55xx Catalyst 85xx Catalyst 65xx

© 1999, Cisco Systems, Inc. BCMSN—2-36 Choosing a Cisco Product (Text Cont.)

© 1999, Cisco Systems, Inc. BCMSN—2-37 The Building Block Approach Building A Switch Block Building BBuilding C Core Block Server Block WAN Block Mainframe Block

© 1999, Cisco Systems, Inc. BCMSN—2-38 Local Event The Switch Block Switch Block 1 Switch Block 2 Access Layer Distribution Layer Access Layer Distribution Layer Broadcast storms are contained to a switch block

© 1999, Cisco Systems, Inc. BCMSN—2-39 The Switch Block (Text Only)

© 1999, Cisco Systems, Inc. BCMSN—2-40 Switch Block Characteristics Support one or more subnets/VLANs Subnets terminate at the distribution switch Access devices have redundant links Spanning tree terminates at the switch block boundary

© 1999, Cisco Systems, Inc. BCMSN—2-41 Sizing the Switch Block Type of traffic Number of users Geographic scope of subnets Size of spanning-tree domains

© 1999, Cisco Systems, Inc. BCMSN—2-42 The Core Block A core is required when there are two or more switch blocks

© 1999, Cisco Systems, Inc. BCMSN—2-43 Core Block Characteristics Supports frame, packet, or cell; subnets terminate at the core Layer 2 or Layer 3 devices Distribution to core links should scale n*100 MBps Supports various configurations Provides redundant paths for each switch block

© 1999, Cisco Systems, Inc. BCMSN—2-44 Core Block Characteristics (Text Only)

© 1999, Cisco Systems, Inc. BCMSN—2-45 A Collapsed Core Switch Block 2 Access Layer Distribution/Core Layer Switch Block 1 Access Layer Distribution/Core Layer Core Connectivity

© 1999, Cisco Systems, Inc. BCMSN—2-46 Switch Block 2 Access Layer Distribution/Core Layer Switch Block 1 Access Layer Distribution/Core Layer Core Connectivity A Collapsed Core (Cont.)

© 1999, Cisco Systems, Inc. BCMSN—2-47 The Dual Core Switch Block 2 Switch Block 1 Core Block Subnet ASubnet B

© 1999, Cisco Systems, Inc. BCMSN—2-48 The Dual Core (cont.) Switch Block 2 Switch Block 1 Core Block Subnet ASubnet B

© 1999, Cisco Systems, Inc. BCMSN—2-49 Sizing the Core Routing protocol limitations Number of distribution switches Number of equal-cost links

© 1999, Cisco Systems, Inc. BCMSN—2-50 Layer 2 Backbone Scaling Spanning tree prohibits core interconnections Equal-cost path limits number of independent core switches

© 1999, Cisco Systems, Inc. BCMSN—2-51 Layer 3 Backbone Scaling Fast convergence Load balancing No peering problems Performance/cost issues

© 1999, Cisco Systems, Inc. BCMSN—2-52 Campus Network Example M1 M2 M P1 P2 P XY ABC North BuildingSouth Building D

© 1999, Cisco Systems, Inc. BCMSN—2-53 Campus Network Example (cont.) M1 M2 M P1 P2 P XY ABC North BuildingSouth Building D

© 1999, Cisco Systems, Inc. BCMSN—2-54 Campus Network Example (cont.) M1 M2 M P1 P2 P XY ABC North BuildingSouth Building D

© 1999, Cisco Systems, Inc. BCMSN—2-55 Campus Network Example (cont.) M1 M2 M P1 P2 P XY ABC North BuildingSouth Building D

© 1999, Cisco Systems, Inc. BCMSN—2-56 Written Exercise Task 1: Describe Layer 2, 3, 4, and Multilayer Switching functions Task 2: Identify the switch layer solution for a given network requirement Task 3: Given a set of user requirements, identify the correct Cisco product solution

© 1999, Cisco Systems, Inc. BCMSN—2-57 Summary Types of traffic affect network performance Device location affects traffic patterns Additional bandwidth is not the solution Multilayer switching combines both Layer 2 and Layer 3 functionality in the same device Multilayer design model is scalable Each component of the multilayer design has a specific function Redundant links provide a fault-tolerant framework

© 1999, Cisco Systems, Inc. BCMSN—2-58 Review Discuss the various trends that have forced a redesign of campus networks. Describe the different switching technologies and how they enable Multilayer Switching. Explain the multilayer model and how it affects traffic flows in the network.

© 1999, Cisco Systems, Inc. BCMSN—2-59 Review (text cont.)

© 1999, Cisco Systems, Inc. BCMSN—2-60 Review (text cont.)

© 1999, Cisco Systems, Inc. BCMSN—2-61 Review (text cont.)

© 1999, Cisco Systems, Inc. BCMSN—2-62 Blank for pagination