Internet Connection Sharing provides networked computers with the ability to share a single connection to the Internet. This article describes the Internet Connection Sharing feature in Microsoft Windows XP.

Note This article is for informational use only, and because of this, it may not contain troubleshooting information. For problem-solving information that is related to Internet Connection Sharing, try searching the Microsoft Knowledge Base again by using the following query words and keywords:

•	internet and connection and sharing
•	dun and modem and isp (if one or more of these words relates to your issue or question)

For additional information about how to more effectively search by using keywords, click the following article number to view the article in the Microsoft Knowledge Base:

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With Internet Connection Sharing, you can connect computers on your home or on your small office network to the Internet over a single connection. For example, if you turn on Internet Connection Sharing on a computer that connects to the Internet by using a dial-up connection, other computers on the network can connect to the Internet through the dial-up connection on the Internet Connection Sharing host.

You can use Internet Connection Sharing to permit yourself and others on your local area network (LAN) to perform different tasks at the same time. For example, one person can send and receive e-mail messages, while another person downloads a file, and yet another person browses the Internet. You can also gain access to your corporate e-mail accounts from a client computer while others on your LAN cannot. You can use Web-enabled programs (such as downloading updates) and Microsoft NetMeeting and other video conferencing programs.

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Internet Connection Sharing capabilities

•	Multiple users can gain access to the Internet through a single connection by using dial-up connections and by using local networking.
•	Connected devices receive transparent network configuration by using Domain Name System (DNS) and Dynamic Host Configuration Protocol (DHCP) to resolve Internet names.
•	Any IP-attached device can connect, including earlier Microsoft Windows-based clients, non-Windows-based clients, Microsoft Windows 98-based clients, Microsoft Windows 2000-based clients, and Microsoft Windows XP-based clients with no additional client software required.
•	Connected devices and software have comprehensive protocol support. For example, you can play Internet games without additional configuration, or you can use Point-to-Point Tunneling Protocol (PPTP) and Virtual Private Networking (VPN) to gain access to your corporate network.

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Windows support for Internet Connection Sharing

To connect multiple computers to the Internet through a single Internet connection, you must turn on Internet Connection Sharing on the computer that you want to use as the Internet Connection Sharing host. Other computers on your LAN can then gain access to the Internet through the connection on the Internet Connection Sharing host computer.

Note Internet Connection Sharing is a built-in feature of Microsoft Windows and is not a component that is available for download. In addition to Windows XP-based computers, you can turn on Internet Connection Sharing on computers that are running Microsoft Windows 98 Second Edition, Microsoft Windows Millennium Edition (Me), and Microsoft Windows 2000.

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Internet Connection Sharing components

The following is a list of Internet Connection Sharing components:

•	DHCP Allocator. A simplified DHCP service that assigns the IP address, default gateway, and name server on the local network.
•	DNS Proxy. Resolves names on behalf of local network clients and forwards queries.
•	Network Address Translation (NAT). Maps a block of private addresses to a set of public addresses. NAT tracks private-source IP addresses and public-destination IP addresses for outbound requests. It changes the IP address information and edits the required IP header information dynamically.
•	Auto-dial . Automatically dials connections.
•	Application Programming Interfaces (APIs). For configuration, status, and dial control for programs.

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Set up a network with Internet Connection Sharing

Your Internet Connection Sharing network is a type of local area network that relies on a single computer that is referred to as a gateway through which all other computers and TCP/IP-capable devices connect to the Internet.

The hardware and software that you must have to set up a home network includes the following:

•	A primary computer (gateway) that provides network connectivity to the Internet. This computer must be running Windows XP, Windows 2000, Windows Millennium Edition (Me), or Windows 98 Second Edition with Internet Connection Sharing turned on.
•	One or more computers that are running Windows 95, Windows 98, Microsoft Windows NT 4.0, Windows 2000, Windows XP, or other TCP-IP enabled client software.
•	Devices that can connect to the Internet.
•	A network connection device for each computer.
•	Cabling and hubs, depending on the type of connection devices that you use.
•	A single modem (or an ISDN or ADSL line) for the whole network.
•	Internet browser software and TCP/IP drivers installed on each device that shares the connection.

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Turn on Internet Connection Sharing

Before you can turn on Internet Connection Sharing on a host computer, the computer must have two network connections present. One network adapter configured to connect to the internal home or small office network, and another connection that is using a 56K modem, ISDN, DSL, or cable modem to connect the small home or office network to the Internet.

For step-by-step instructions to turn on Internet Connection Sharing, click the following article number to view the article in the Microsoft Knowledge Base: For additional information about how to turn on Internet Connection Sharing, click the following article numbers to view the articles in the Microsoft Knowledge Base: If you are setting up a home or a small office network, you can use the Network Setup Wizard to turn on Internet Connection Sharing. The Network Setup Wizard automatically provides all the network settings that you must have to share one Internet connection with computers on your network.

For additional information about the Network Setup Wizard, click the following article number to view the article in the Microsoft Knowledge Base:

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For additional information about home networking and about Internet Connection Sharing in Windows XP, click the following article number to view the article in the Microsoft Knowledge Base: For additional information about how to configure Internet Connection Sharing in Windows XP for an Internal PPTP Server, click the following article number to view the article in the Microsoft Knowledge Base:

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