Designing Enterprise Edge Connectivity © 2004 Cisco Systems, Inc. All rights reserved. Designing the Classic WAN Module ARCH v1.23-1

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Enterprise Needs from the WAN Bandwidth Link quality Reliability Data link protocol characteristics Always-on or on-demand characteristics Cost

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Typical Large Enterprise WAN

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Branch Office WAN Redundancy depends on the criticality of the site and the number of users affected. Branch offices normally do not act as aggregation points.

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Regional Office WAN Includes multiple load-sharing links to the central site Aggregates traffic from the branch and sends it to the central site

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Enterprise WAN Backbone Generally a full mesh between sites Must incorporate aggregation from the regional offices Server farms are normally accessed through the network

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Criteria for Selecting a Service Provider Price Speeds supported Features supported Geographies covered Service level agreements –Bandwidth –Round-trip response –Network services –Loss

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Data Link Layer Technology Characteristics Bandwidth Supported Media Quality Network Delay Tolerance Protocol Reliability Relative Cost PPP ModerateLow ModerateLow Frame Relay ModerateHighLow Moderate ATM High Low Moderate MPLS High Low Moderate X.25 Low High Moderate

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Physical Layer Technology Characteristics Bandwidth Range Link Quality On Demand/ Always On Cost Factors Leased Line Any Media dependent Always On Bandwidth related DSL Moderate Always On Market pricing Dial-Up Low On Demand Connection frequency and duration ISDN Moderate Control: Always On Link: On Demand Connection frequency and duration Optical High Always On Distance and bandwidth

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Selecting WAN Features PPP –Multilink PPP or PPP Frame Relay –Number of ports –CIR –Maximum burst size ATM –Number of ports –Service Class (one of CBR, ABR, UBR, RT-VBR, NRT-VBR) X.25 –Rate –Number of ports

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Selecting Cisco Edge Routing Solutions

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Routing Protocol Considerations for the Site-to-Site WAN HierarchicalFlat Point-to- Point Point-to- Multipoint (Frame Relay) Static Routes XX EIGRP XXXX OSPF XXX RIPv2 XXXX

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Routing Protocol and IP Addressing Design Considerations EIGRP –Reduce the query range via summarization, distribution lists, and stubs. –Allow for route summarization. OSPF –Areas organize and allow division of large networks. –Create an address hierarchy to match the topology. –Make addressing contiguous with respect to topology. RIPv2 –Use a limited number of hops. –Allow for route summarization.

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Identifying an IP Addressing Strategy Determine the size of the network. How big is the network? How many locations are in the network and what are their sizes? What class of addresses and how many networks can be obtained from the public number authority? How many addresses will be needed throughout the network?

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Identifying an IP Addressing Strategy (Cont.) Determine if you need private or public addresses. –Are private, public, or both address types required? –How many end systems need access to the public network only? –How many end systems need to be visible to the public network also? –How and where will you cross the boundaries between the private and public addresses? Determine how to implement the IP addressing hierarchy. –Is hierarchy needed within an IP addressing plan? –What are the criteria to divide the network into route summarization groups? Is a multilevel hierarchy needed?

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Example: Branch Office WAN

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Site-to-Site Regional Office to Campus Backbone

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Site-to-Site Completed Network

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Summary An enterprise site-to-site WAN network must meet requirements for bandwidth, link quality, reliability, data link protocol characteristics, always-on or on-demand characteristics, and cost. The WAN topology includes the physical and logical WAN topology. The topology is closely related to the geographical structure of the enterprise. Once the bandwidth, redundancy, and service level requirements are defined, you can determine what transport is available to implement the design. Do not be surprised if you have to do some redesign based on features and costs from the service provider. For the data link layer, you will select technologies including PPP, Frame Relay, ATM, and X.25.

© 2004 Cisco Systems, Inc. All rights reserved. ARCH v Summary (Cont.) For the physical layer, you will select physical layer technologies including leased line, DSL, dial-up, ISDN, or optical. After you select the data link and physical layer technologies, you can select specific WAN features. Each data link layer technology has its own WAN features to select. The Cisco Product Advisor is a useful tool for selecting edge routing solutions. The tool is interactive, and provides a list of options from which to choose. The decision about which routing protocols to implement is based on the design goals, the physical topology of the network, and the configuration of links for remote sites. Routing protocol selection is closely related to IP addressing strategies.