Keeping Yourself Up-to-Date Managing and Maintaining Your VPN

167

Chapter 11. A VPN Scenario

If you havent gotten enough of the virtual private network yet, this chapter will cover a real, live, up and running VPN. Weve covered the theory and some general cost-to-benefit analysis, and now we move on to some actual products working in a production environment. Though we have used specific products here like Ascend and Cisco, you may well find that other solutions better fit your enterprise. In other words, this chapter isnt VPN law, just an example.

11.1 The Topology

Well call the company in this case study Immediate PC. It manufactures and sells computer parts and peripherals. About a year ago, Immediate PC made the commitment to standardize its network communications between its various sites over the Internet. Naturally, their main concerns were security, cost, and reliability. Communication needs at Immediate PC are like those at most companies. Sales agents in the field must communicate with manufacturing managers at the factories to order and ensure production of needed stock. The retail store arm of the company also communicates with shipping, manufacturing, and several other departments on a daily basis. Various factories and other divisions across the country must send and obtain data to keep their operations flowing. Several different platforms are used at various levels of the organization. The main corporate network is comprised of Windows NT servers and Windows NT or Windows 95 workstations. Additionally, there are several Unix servers of various flavors. Remote access users employ a variety of operating systems, and a few departments within the main corporate networks use Macintosh systems. Without the Internet, the flow of data and the cost associated with private lines and dial-up access were crippling operations and eating into profits. Having decided to use advanced technology to remedy the situation, Immediate PC migrated gradually from private lines and remote access to a controlled use of the Internet. Research, training, and various levels of approval preceded the move to virtual private networks. After this move, the company reduced the cost of network communication and resolved several communications problems. What emerged was the virtual private network detailed in the network diagram at the end of this chapter. The chosen architecture links a central corporate office with various remote offices, large and small, in addition to a gaggle of remote access users. The following sections detail what was needed in connections to the Internet, equipment, software, and virtual private network solutions.

11.2 Central Office

The central office is the natural source of information about products and operations. Security is critical. Besides the VPN, several other Internet services are centralized here, including the 168 corporate web, email, and FTP servers. The company web- based Intranet is also centralized at the main office.

11.2.1 Network Connections

The central office maintains two T1 connections through two separate national Internet providers. This provides redundancy and gives other connecting sites a variety of network paths over which they can reach the central office. The T1 connections allow enough bandwidth for all sites to connect to the central network with adequate response time over the VPN, in addition to supporting these other services.

11.2.2 Hardware and Operating System

Routing traffic from the T1, the company has a Cisco 4500 Internet router. This is a robust and expandable router that can handle up to four T1s for a large network. Likewise, it can encapsulate and route a variety of protocols, from IP to AppleTalk. For broad coverage of VPN solutions, the main office is running PPTP on Windows NT servers. Secondarily, there is a Unix server and an Ascend MAX remote access hub, both running PPTP.

11.2.3 VPN Package

The central office must run three VPN servers to give their connecting networks a variety of solutions. The large branch offices require a stable and fast network-to- network VPN. For this high-bandwidth task, the Cisco PIX firewall was chosen. In addition to being a robust firewall solution, the PIX enables the various large networks to encrypt data traffic from one network to the other. This, combined with the routing power of the Cisco routers, allows each network a variety of protocols, while maintaining a secure connection. Other network-capable VPNs like the AltaVista Tunnel didnt provide the robust and fast VPN solution for these large remote networks. Other remote users dialing in either to the Internet or one of the branch offices are using PPTP.

11.3 Large Branch Office

Other Internet services are maintained at some of the large branch offices, such as web and FTP servers.

11.3.1 Connection

Large branch offices around the country are connected to the Internet via fractional T1 or full T1, depending on the size of their networks and the level of network activity. Their network connections are through one of the two national providers that connect the central office to the Internet. This allows for a faster connection to the central office. This strategy lessens the amount of hops necessary to reach corporate office Internet connections.

11.3.2 Hardware and Operating System

A Cisco 2500 router is needed to support fractional to full T1 connections for these networks. Sites use PPTP and Windows NT or Unix servers for dial-up users and smaller connecting networks.