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Network interfaces

Updated: January 21, 2005

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Network interfaces

Network interfaces enable any server running Routing and Remote Access to communicate with other computers over private or public networks. Network interfaces have two aspects that relate to Routing and Remote Access: the physical hardware, such as a network adapter, and the network interface configuration.

Physical hardware

Network interface hardware, commonly called network adapters, can be any adapter that plugs into the system bus of a computer and allows that computer to connect to a network. Most servers running Routing and Remote Access have at least two network adapters. This is required if the server running Routing and Remote Access is acting as a router between two network segments. A server that has two or more network adapters connecting to separate networks is called multihomed.


  • Because multihomed servers are accessible from more than one network, they have more security requirements than a server that is connected to a single network. Each network interface must be configured correctly in order to protect the server and the private networks to which the server connects. For more information, see Security information for routing and Security information for remote access.

The server running Routing and Remote Access usually detects all network adapters automatically when the Routing and Remote Access Server Setup Wizard is run. If you install an additional network adapter after the wizard has been run, you can add and configure the interface using Routing and Remote Access. For more information, see Add a routing interface.

Network interface configuration

In Routing and Remote Access, network interfaces fall into the following categories:

  • Private interface. A private interface is a network adapter that is physically connected to a private network. Most private networks are configured with a private network IP address range, and the private interface is also configured with a private address. Because a private network is, in theory, composed of known users and computers, you generally have fewer security considerations for a private interface than for a public interface. For more information, see Internet private addresses.

  • Public interface. A public interface is a network adapter that is physically connected to a public network, such as the Internet. The public interface is configured with a public IP address. You can configure a public interface to perform network address translation (NAT). Because a public interface is theoretically accessible by anyone on the public network, security considerations are generally higher for a public interface than for a private interface.

  • Demand-dial interface. Demand-dial interfaces connect specific routers on either public or private networks. A demand-dial interface can be either on-demand (activated only when needed) or persistent (always connected). For more information, see Demand-dial routing.

In addition to configuring each network interface as a public, private, or demand-dial interface, you can configure packet filters, addresses, and other options for network interfaces. Some options for public interfaces, such as Basic Firewall, are not available for private interfaces. For more information about the kind of configuration you might want to consider and example implementations, see Routing Scenarios and Remote Access Scenarios.

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