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ISA Server 2000 provides several services for your Small Business Server network, including routing and network address translation (NAT) services and firewall service. To protect your local network from Internet access, it is recommended that you install ISA Server. Additionally, several of the Internet
connection types supported by the Small Business Server Internet Connection Wizard require ISA Server. For more information, see the “”Network Topologies”” section later in this white paper.
When you run Setup or the Small Business Server Internet Connection Wizard, ISA Server is configured as follows:During Setup, ISA Server is installed in integrated mode, which includes both the firewall mode and cache mode, so you can secure your network.During Setup, the local address table (LAT) of ISA Server is configured to include the IP range of your internal network. ISA Server uses the LAT to determine if a network request should be routed to the Internet or to a local computer. If you are using a router to connect to the Internet and it has a different IP address range than your local network, make sure that the router’s IP address is not included in the LAT, or client computers will be unable to access the Internet.During Setup, your Small Business Server’s internal domain name is added to the local domain table (LDT) of ISA Server. The LDT is a table of all the domain names in the internal network served by the ISA Server computer. When a client computer makes a request to another computer, name resolution is required. The client computer first checks the LDT. If the domain name does not appear in the LDT, the client computer then requests that ISA Server resolve the domain name on its behalf. For example, if your domain name is smallbusiness.local, the LDT would contain smallbusiness.local.By running the Small Business Server Internet Connection Wizard, the internal and external routing rules are defined for ISA Server to monitor incoming and outgoing Web requests.By running the Small Business Server Internet Connection Wizard, you have the option of enabling the Web server filter to allow incoming connections for Hypertext Transfer Protocol (HTTP) and Hypertext Transfer Protocol Secure (HTTPS) requests for your Web site.
ISA Server 2000 provides firewall functionality by monitoring all incoming and outgoing Internet network traffic. A firewall protects your local network from unauthorized Internet access by permitting only packets that meet predefined criteria to reach the local network. To configure the criteria for which packets are permitted to access the Small Business Server computer, run the Small Business Server Internet Connection Wizard. When you run the wizard, you can define the types of network traffic you want to allow access to and from your local network. For example, you can permit e-mail traffic to and from the Internet.