Internet Connection Sharing PDF Print
Internet Connection Sharing (ICS) is the name given by Microsoft to a feature in recent versions of its Windows operating system (as of Windows 98 Second Edition) for sharing a single Internet connection on one computer between other computers on the same local area network. It makes use of DHCP and Network address translation (NAT).

ICS routes TCP/IP packets from a small LAN to the Internet. ICS maps individual IP addresses of local computers to unused port numbers in the TCP/IP stack. Due to the nature of the NAT, IP addresses on the local computer are not visible on the Internet. All packets leaving or entering the LAN are sent from or to the IP address of the external adapter on the ICS host computer.

On the host computer the shared connection is made available to other computers by enabling ICS in Network Connections, and other computers that will connect to and use the shared connection.

ICS offers configuration for other standard services and some configuration of NAT.

Criticism

However, while ICS makes use of DHCP, there is no way to review DHCP leases using ICS. The service is also not customizable in terms of which addresses are used for the internal subnet, and contains no provisions for bandwidth limiting or other features common to more advanced systems, that can be also combined with Wi-Fi and dial-up mobile modems.

The server will always have the IP address 192.168.0.1 and will provide NAT services to the whole 192.168.0.x subnet, even if the address on the client was set manually, not by the DHCP server.

Troubleshoot

Besides make sure that the firewall settings are correct, for Windows XP host with more than one Ethernet interface cards and a wireless WAN connection, bridging the Ethernet interface cards may help eliminating some ICS malfunction problems. It is found from repeated testing that without bridging, ICS may not work correctly if only one of the several Ethernet cards is selected from the wireless connection's Internet Connection Sharing option drop down box. This problem may have been solved in later versions of Microsoft Windows products.


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