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This chapter is from the book

This chapter is from the book

Setting Up a Local ISA VPN Server

In the section VPN Support, I mentioned that the ISA Server offers wizards to configure VPNs in two common scenarios: a branch office connecting to another branch office, and an employee connecting to the corporate network. To create a VPN tunnel between two branch offices across the Internet, you will use the Local ISA Server VPN Wizard and the Remote ISA Server VPN Wizard. Later, you will learn how to configure your server for the second scenario so that the users can create a VPN tunnel to access resources on your corporate network.

To create a VPN tunnel between two networks across the Internet, you need to run the Local ISA Server VPN Wizard on one end of the tunnel and the Remote ISA Server VPN Wizard on the other end. For example, if you want to connect two branch offices in Denver and Miami, run the Local ISA Server Wizard first on the ISA Server in Denver, create a .vpc file, and then use this .vpc file when you run the Remote ISA Server Wizard in Miami. Here's the step-by-step procedure to create the first end of the tunnel.

  1. In the ISA Server Management console, click on Server and Arrays, <your server name>, Network Configuration.

  2. Right-click Network Configuration and select Set Up Local ISA VPN Server to start the Local ISA VPN Wizard.

  3. If Routing and Remote Access service is not running on the ISA Server, you will see a message telling you that the Routing and Remote Access service must be started before the VPN setup wizard can continue. Click Yes to start the service.

  4. On the ISA VPN identification screen, type a short name to identify the local network, such as DENVER. Also, type a name for the remote network, such as MIAMI. Notice that the connection will be identified as DENVER_MIAMI.

  5. On the ISA VPN Protocol screen, select a tunneling protocol that will be used for establishing a VPN. You can use L2TP, PPTP, or both. For our example, we will use PPTP.

  6. On the Two-way Communication screen, select the box Both the Local and Remote ISA VPN Computers Can Initiate Communication, as shown in Figure 3.14, if you want either end to be able to initiate connection. Otherwise, leave the box unchecked so only the remote computer can initiate communication. Also, in this screen enter an IP address and the name of the remote VPN computer or domain. If you use the domain name, make sure you use the NT-style name; for example, TechGalaxy instead of TechGalaxy.net.

  7. Figure 3.14 Enabling two-way communication.

  8. On the Remote VPN Network screen, enter the range of IP addresses on the remote VPN network that can be accessed by the local VPN computer. This will be the range of computers in Miami that can be accessed by the local VPN in Denver. The figure shows one range of IP addresses. You could add additional ranges of addresses if necessary.

  9. On the Local VPN Network screen, select the IP address of the external interface of the local VPN computer and then specify the range of IP addresses on the local VPN that can be accessed by the remote VPN computer, as shown in Figure 3.15. The remote VPN computer in Miami will use the IP address of the local VPN computer in Denver to create the tunnel. Once connected, it will be able to access computers in Denver that fall within the range of IP addresses that you have specified here. These IP address ranges are also used to create static routes that are managed through the Routing and Remote Access console.

  10. Figure 3.15 Configuring local VPN options.

  11. On the ISA VPN Computer Configuration File screen, provide the name of the configuration file that will be used to configure the remote VPN computer. The file will be saved with a .vpc extension, for example denver_miami.vpc. Also provide a password to encrypt this file so that only the administrator of the remote VPN computer will be able to access it.

  12. On the final screen of this wizard click on Details and verify that everything looks right.

  13. Click Finish to complete the wizard.

This will create a Routing and Remote Access demand-dial interface. To verify that the interface was created properly, go to the Routing and Remote Access console in Administrative Tools on the ISA Server computer. Click on the server name and then click Routing Interfaces. In the right-hand pane, verify that a demand-dial interface called DENVER_MIAMI exists. Although you created this interface in ISA Management console, any changes to this interface must be made in Routing and Remote Access.

Remember, now you need to run the Remote ISA VPN Wizard on the remote VPN computer to create the other end of the tunnel.

Setting Up a Remote ISA VPN Server

The procedure for setting up a remote ISA Server VPN is somewhat different to the one discussed previously. At the remote location in Miami, you will use the .vpc file that was created in Denver to create the second end of the tunnel. Here's the step-by-step procedure:

  1. In the ISA Server Management console, click on Server and Arrays, <your server name>, Network Configuration.

  2. Right-click Network Configuration and select Set Up Remote ISA VPN Server to start the Remote ISA VPN Wizard.

  3. In the ISA VPN Computer Configuration File screen enter the path to the file in the File Name box, such as A:\denver_miami.vpc. This file contains configuration information about the remote VPN computer. Also, in the Password box, enter the password that was used when this file was created so that the file can be decrypted.

  4. On the final screen of this wizard click on Details and verify that everything looks right.

  5. Click Finish to complete the wizard.

When you complete the wizard, it will create the demand-dial interface, configure packet filtering for security, and configure static routes so that traffic from the local network can be forwarded to the remote network. Again, as in the previous section, the interface is created and can now be managed from the Routing and Remote Access console instead of the ISA Management console.

At this point, you have created both ends of the VPN tunnel, and users in Denver and Miami will be able to communicate using it.

Setting Up ISA Server to Accept Client VPN Requests

So far we've talked about the scenario where two branch offices can be connected through a VPN tunnel. Let's look at the second scenario that is used for clients to connect to your corporate network.

ISA server offers this additional wizard that configures your server to accept connections from remote clients. This enables users to create VPN connections from their home computers to the corporate network so they can access resources on the network. Typically, mobile users benefit from this type of connectivity because they can dial-in to their local ISP and then create a VPN tunnel to their company network. This saves money on long distance charges and offers users secure connectivity to the company resources.

Here's how you set up ISA Server to accept VPN requests from the clients:

  1. In the ISA Server Management console, click on Server and Arrays, <your server name>, Network Configuration.

  2. Right-click Network Configuration and select Allow VPN Client Connections to start the ISA VPN Configuration Wizard.

  3. Click Details to see configuration information and then click Finish to complete the wizard. Congratulations! You just completed the world's shortest wizard with only two steps—start and finish.

  4. If you are prompted to restart the Routing and Remote Access service, click Yes to continue.

What did this wizard do in the background? It configured your Routing and Remote Access server as a VPN server so clients can be properly authenticated. It also automatically configured IP packet filters for you. There is one thing that the wizard doesn't do, and you need to take care of that business manually. You need to give the appropriate rights to the user to dial in to your network. This can be achieved either by configuring user account properties in Active Directory Users and Computers, or through Remote Access Policies.

Allowing Outbound PPTP Access

The previous situation applied to external users coming into your network through the Internet. If your internal clients have a need to create VPN tunnels from the internal network to a server on the Internet, you can enable outbound PPTP on the ISA Server computer. For example, you have some consultants working at your site that require access to their e-mail on their corporate network server. You can allow PPTP through the ISA Server so they can securely access their corporate server and read their e-mail. Here's how to enable the PPTP option:

  1. In the ISA Server Management console, click on Server and Arrays, <your server name>, Access Policy, IP Packet Filters.

  2. Right-click IP Packet Filters and click on Properties.

  3. On the PPTP tab, check the box PPTP Through ISA Firewall.

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