Wide Area Network Design Requirements
Terrapin wants to remove the leased lines and 3174 cluster controllers and network its sales offices using public Frame Relay service. The new WAN must seamlessly integrate into the existing corporate internetwork.
As the design engineer, you are responsible for the OSPF design and implementation, TCP/IP addressing scheme, and router implementation of this frame relay network. To construct a scalable OSPF network capable of meeting both the present and future requirements, you need to gather the necessary information from the appropriate
Determining the Frame Relay PVC Architecture
The corporate engineering
Each spoke or remote sales office will have a 56KB local circuit installed into the frame relay POP with a single 32K CIR PVC provisioned to a T1 circuit which will be installed on a central hub router at the corporate Headquarters and data center facility in Tennessee. The CIR on the T1 circuit will be 384K.
Determining if There Will Be Multi-Protocol Support
The WAN network must support Novell IPX in addition to TCP/IP since it is on the customers LANs. The corporate IS manager indicates that no native SNA will need to be supported on this network as all the IBM 3174 controllers will be removed after conversion to frame relay. Mainframe access will be accomplished using TCP/IP directly from terminal emulation software running TN3270 (Telnet) at the Regional Sales Offices
Determining the Application Data Flow
The IS manager
Determining the Number of Routers
There will be 25 routers on this frame relay network with a potential 10% increase (3 routers) over the next three
Determining TCP/IP Addressing
Terrapin Pharmaceuticals is allocating TCP/IP addresses from the private RFC 1918 space. All existing LANs are
Determining Internet Connectivity
Terrapin Pharmaceuticals currently has Internet connectivity through a firewall segment. The default route or gateway of last resort is propagated into IGRP from a central router on the internal network to all other IGRP-speaking routers. A registered class C address has been obtained and is deployed as the Internet DMZ segment. This is the only address that is announced to the Internet from Terrapins Internet Cisco 4700 router, as the firewall has proxy and Network Address Translation (NAT) capabilities.
Determining Enterprise Routing Policies
After speaking with the managers of the IS department, you discover that they intend to migrate the network from IGRP to OSPF on the existing Cisco router base in the near future. Thus, the frame relay network must run OSPF and integrate seamlessly into the eventual corporate OSPF network architecture. Because no timeframe for the campus OSPF conversion can be determined, your network must integrate into the IGRP network upon installation for an undetermined period of time.
Establishing Security Concerns
The company plans to use OSPF password-authentication when the network is converted to OSPF from IGRP. The security manager indicates that a single password will be sufficient across all OSPF-speaking router links.
After evaluating all of Terrapins requirements, Figure 7-27 illustrates the proposed OSPF network design.
OSPF Network Design
This section will discuss some of the design topics to consider within this case study.
You are able to obtain a contiguous block of 32 class C ( /24 or 255.255.255.0 mask) subnets for this network from the IP address manager. The address block is 172.17.64.0/19 , which will allow clean summarization into the backbone area once the corporate network converts to OSPF. (This occurs because all of the frame relay network LAN and WAN addresses will be summarized as one route ( 172.17.64.0/19 ) once the backbone routers are converted to OSPF as show in Figure 7-28.)