The Topology A VPN Scenario

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.