How to Troubleshoot Internet Connection Sharing Problems

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WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

When you use ICS, you can share one Internet connection between two or more computers. Before you install or use ICS, you should contact your Internet service provider (ISP) or read your ISP's Terms and Conditions of use policy to determine if you are permitted to share your connection.

For additional information about ICS, click the article number below to view the article in the Microsoft Knowledge Base:

234815 (http://support.microsoft.com/kb/234815/EN-US/) Description of Internet Connection Sharing

To install ICS:

1.	Click Start, point to Settings, click Control Panel, and then double-click Add/Remove Programs.
2.	Click Internet Tools on the Windows Setup tab, and then click Details.
3.	Click to select the Internet Connection Sharing check box, click OK, and then click OK again.
4.	Follow the instructions to run the ICS wizard.

NOTE: You should only install ICS on the computer that you use to connect to the Internet. This computer is called the "host" computer. The other computers on the local area network (LAN) that use the host to connect to the Internet are called "client" computers.

For additional information about ICS requirements, click the article number below to view the article in the Microsoft Knowledge Base:

230140 (http://support.microsoft.com/kb/230140/EN-US/) Only One Internet Connection Sharing Host Is Required on a LAN

NOTE: The term "dial-up adapter" is used in this article to refer to your modem. This term may also refer to an Integrated Services Digital Network (ISDN) or Asymmetric Digital Subscriber Line (ADSL) device.

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Host Configuration

To troubleshoot ICS, verify that the correct components are installed on the host after you install ICS. Check for the following two components in Network properties, where adapter is your dial-up adapter or your network adapter:

•	TCP/IP(Shared)->adapter
•	TCP/IP(Home)->adapter

To check the components in Network properties:

1.	Click Start, point to Settings, click Control Panel, and then double-click Network.
2.	On the Configuration tab, view the The following network components are installed box to verify that both the TCP/IP(Shared) and TCP/IP(Home) components are listed.

If either of the components appear in Network properties but do not have the (Home) and (Shared) reference, ICS is not installed correctly and does not work correctly. You may need to remove and then reinstall ICS to resolve this issue.

For additional information about the ICS entries in Network properties, click the article number below to view the article in the Microsoft Knowledge Base:

236465 (http://support.microsoft.com/kb/236465/EN-US/) Description of How ICS Appears in Network Properties

The TCP/IP(Shared) component should be the adapter that you use to connect to the Internet and the TCP/IP(Home) component should be the adapter that you use to connect to your LAN. If the TCP/IP(Shared) component is not in the The following network components are installed box, the host and client computers cannot connect to the Internet. If the TCP/IP(Home) component is not in the The following network components are installed box, the host and client computers may not be able to connect to each other on the LAN.

NOTE: If you know the adapter that you use to connect to the Internet and the adapter that you use to connect to the LAN, you can skip the following Determining the TCP/IP(Shared) and the TCP/IP(Home) adapter section.

How to Determine the TCP/IP(Shared) and TCP/IP(Home) Adapters

•	Standard Dial-Up Networking Connections For a standard Dial-Up Networking connection, the Microsoft dial-up adapter should be listed in Network properties. To determine if Dial-Up Networking is used to connect to the Internet, check for an icon for your ISP in the Dial-Up Networking folder. To view the Dial-Up Networking folder, double-click My Computer, and then double-click the Dial-Up Networking folder. For a standard Dial-Up Networking connection, the following components should be listed in Network properties for the host computer: • TCP/IP(Shared)->Dial-Up Adapter • TCP/IP(Home)->Network Adapter • Third-Party Internet Dialer Connections To determine if you are using a third-party dialer to connect to the Internet, check Network properties to view the third-party dialer's dial-up adapter. For ICS to work correctly with a third-party dialer, the dialer software must use a 32-bit dial-up adapter. Some ISPs use their own dialer to connect to the Internet, for example, America Online (AOL). For a third-party dialer connection, the following components should be listed in Network properties for the host computer, where Third-Party Dialer Adapter is the name of the third-party dialer adapter, and is the name of the network adapter: • TCP/IP(Shared)->Third-Party Dialer Adapter • TCP/IP(Home)->Network Adapter For additional information about how to use third-party dialers with ICS, click the article numbers below to view the articles in the Microsoft Knowledge Base: 230233 (http://support.microsoft.com/kb/230233/EN-US/) How to Use AOL with Internet Connection Sharing 229978 (http://support.microsoft.com/kb/229978/EN-US/) ICS Cannot Autodial 3rd-Party Internet Dial-Up Connections NOTE: For devices that use a network adapter, some ISP's record the adapter address, which is often referred to as the "MAC address" of the network adapter. Your ISP may only allow you to connect to the internet with that specific network adapter. If you want to use a different network adapter, you may need to contact your ISP for additional assistance.
•	Unidirectional devices For unidirectional devices, such as one-way cable modems, you must have a connection to a source to send data and a connection to a source to receive data. ICS does not work correctly with this type of configuration.For additional information about one-way adapters, click the article number below to view the article in the Microsoft Knowledge Base: 231648 (http://support.microsoft.com/kb/231648/EN-US/) ICS Does Not Function with Unidirectional Adapters
•	Two-way cable modems For a two-way cable modem, the cable modem requires a network adapter for the host computer. This configuration requires that you have two network adapters installed in your computer, one for the cable modem and one for the LAN. For a cable modem connection, the following components should be listed in Network properties for the host computer, here the TCP/IP(Shared) is the network adapter connected to the cable modem, and TCP/IP(Home) is the network adapter connected to the LAN: • TCP/IP (Shared)->Network Adapter1 • TCP/IP (Home)->Network Adapter2
•	ADSL devices For an external asymmetric digital subscriber line (ADSL) device, the ADSL device requires that there is a network adapter installed in the host computer. This configuration requires two network adapters to be installed in the computer, one for the cable modem and one for the LAN. For a external ADSL device connection, the following components should be listed in Network properties for the host computer, where TCP/IP(Shared) is the network adapter that is connected to the ADSL device, and TCP/IP(Home) is the network adapter that is connected to the LAN: • TCP/IP(Shared)->Network Adapter1 • TCP/IP(Home)->Network Adapter2 NOTE: For an internal ADSL device, the ADSL device uses the standard dial-up adapter to connect to the Internet. Internal ADSL devices should function the same as standard dial-up networking connections. This can also be true for external ADSL devices, such a those that connect through USB ports. You will normally see a reference to a PPPoE (Point-to-Point Protocol over Ethernet) or PPPoA (Point-to-Point Protocol over ATM). You should also see TCP/IP (Shared), Dial-up Adapter (as listed above), or Modem Connections. For more information, see the following articles in the Microsoft Knowledge Base: 273587 (http://support.microsoft.com/kb/273587/EN-US/) How to Configure ICS for Use with DSL Connections That Use PPPoE 265728 (http://support.microsoft.com/kb/265728/EN-US/) Internet Connection Sharing Requires Two Network Adapters
•	ISDN devices For an Integrated Services Digital Network (ISDN) device, both internal and external ISDN devices use the dial-up adapter to connect to the Internet. ISDN devices should function the same as standard dial-up networking connections.

Using the Icssetup.log File

To determine which adapters the Internet Connection Sharing wizard identified as potential Shared and Home Adapters, check the Icssetup.log file in the Windows folder. The Internet Connection Sharing wizard checks for possible adapters from the lists of adapters in Network Properties. If problems exist, verify that each of these adapters are also listed under Network Adapters in Device manager.

NOTE: The Internet Connection Sharing wizard will never identify a dial-up adapter as the Home Adapter.

Sample Icssetup.log file

Internet Connection Sharing Setup Log: Wednesday Mar 17 1999
Build Adapter ListBuild Adapter List - found: Dial-Up Adapter
Build Adapter List - found: Linksys LNEPCI II PCI Ethernet Adapter
Build Adapter List - found: Internet Connection Sharing
Find Internal Adapter Candidates, checking: Dial-Up Adapter NOT a
candidate, known special purpose adapter
Find Internal Adapter Candidates, checking: Linksys LNEPCI II PCI Ethernet Adapter IS a candidate
Find Internal Adapter Candidates, checking: Internet Connection Sharing NOT a candidate, known special purpose adapter
Find External Adapter Candidates, checking: Dial-Up Adapter IS a candidate
Find External Adapter Candidates, checking: Linksys LNEPCI II PCI Ethernet Adapter NOT a candidate, only valid Internal adapter
Find External Adapter Candidates, checking: Internet Connection Sharing NOT a candidate, known special purpose adapter
Find Internal Adapter Candidates, checking: Dial-Up Adapter NOT a candidate, known special purpose adapter
Find Internal Adapter Candidates, checking: Linksys LNEPCI II PCI Ethernet Adapter IS a candidate
Find Internal Adapter Candidates, checking: Internet Connection Sharing NOT a candidate, known special purpose adapter
Loaded external adapter: Dial-Up Adapter
Loaded internal adapter: Linksys LNEPCI II PCI Ethernet Adapter

TCP/IP(Home) and TCP/IP(Shared) Appear on the Wrong Adapters

To resolve this issue, follow these steps:

1.	Click Start, point to Settings, click Control Panel, and then double-click Internet Options.
2.	On the Connections tab, click Sharing.
3.	Under Connect to the Internet using, select the adapter for your Internet connection from the list.
4.	Under Connect to my home network using, select the adapter for your LAN from the list.
5.	Click OK, click OK again, and then restart your computer when you are prompted.

If the Sharing button is not present, this can be caused by the wrong versions of the Inetcpl.cpl and Inetcplc.dll files. For additional information on this issue, click the article number below to view the article in the Microsoft Knowledge Base:

236152 (http://support.microsoft.com/kb/236152/EN-US/) No Sharing Button After Installing Internet Connection Sharing

NOTE: If you remove or reinstall any components that are displayed in Network Properties on the Host, you must also remove and reinstall ICS.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Only One of the TCP/IP Components is Listed in Network Properties

This issue can occur if one or more registry key is damaged. To resolve this issue, follow these steps:

1.	In Network Properties, write down the description of each of the adapters listed.
2.	In Registry Editor, open the following key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Net\ Where is an incremental 4-digit number starting at 0000.
3.	Delete each key where the DeviceDesc entry does not match the description of one of the adapters in Network Properties. If there are multiple keys for the same adapter listed in Network Properties, delete each of the keys and then remove and reinstall the adapter in Device Manager. To remove the adapter in Device Manager, click Start, point to Settings, click Control Panel, double-click System, click the Device Manager tab, double-click Network adapters, click the adapter, and then click Remove.NOTE: You may need the original driver disk or software to reinstall the adapter after you remove it from Device Manager.

TCP/IP(Shared) and TCP/IP(Home) Components Missing

This issue can occur if the Iphlpapi.dll file is the incorrect version or damaged.

To resolve this issue, extract a new version of the file from the Windows 98 Second Edition CD-ROM and then remove and reinstall ICS. To extract the Iphlpapi.dll file, follow these steps:

1.	Click Start, click Run, type sfc.exe in the Open box, and then click OK.
2.	Click Extract one file from Installation disk.
3.	Type iphlpapi.dll in the Specify the system file you would like to restore box, and then click Start.
4.	In the Restore From box, type the drive letter and path to the Windows 98 Second Edition Source CD-ROM folder.
5.	In the Save File In box, type the full path to the \Windows\System folder (for example, C:\Windows\System), and the click OK.
6.	Click OK to use the default backup folder when you are prompted.
7.	Click OK and the quit System File Checker.
8.	Remove and reinstall ICS

Enable DHCP Services on Host

Without a proper IP address, the client will be unable to communicate with the Host computer. If the client computer does not obtain an IP address from the Host, the DHCP service may be disabled. To enable the DHCP services on the Host computer, follow these steps:

1.	On the Windows 98 Second Edition CD-ROM, open the Tools\MTSutil\ICS folder.
2.	Right-click the Dhcp_on.inf file, and then click Install.
3.	Restart Windows.

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Client Configuration

Configure Client for DHCP

To configure the client computer to obtain an IP address from the Host computer, follow these steps:

1.	Click Start, point to Settings, click Control Panel, and then double click Network.
2.	Click the TCP/IP component installed for the Network Adapter on you LAN.
3.	Click Properties.
4.	On the IP Address tab, click Obtain IP address automatically.
5.	On the WINS Configuration tab, click Use DHCP for WINS Resolution.
6.	On the Gateway tab, remove any gateways that may be installed.
7.	On the DNS Configuration tab, click Disable DNS.
8.	Click OK, click OK again, and then click Yes if you are prompted to restart the computer.

If you prefer to assign the client IP information manually, or feel that the DHCP is not functioning properly, refer to the section entitled How to Assign a Static IP Address later in this article.

How to Assign a Static IP Address

Before you can assign a static IP address, you will need the DNS configuration information from your ISP. Or, on the Host computer, click Start, click Run, type winipcfg, and then click OK. Click ICShare Adapter, click More Info, note the DNS server address, and then click OK. After you obtain the DNS setting, follow these steps:

1.	Click Start, point to Settings, click Control Panel, and then double-click Network.
2.	Click the TCP/IP component installed for the Network Adapter on you LAN.
3.	Click Properties.
4.	On the IP Address tab, click Specify an IP Address.
5.	In the IP Address box, type 192.168.0.x (where x is a number between 2 and 254). NOTE: The IP address should be one that is not currently in use by another computer on your LAN.
6.	In the Subnet Mask box, type 255.255.255.0.
7.	On the WINS Configuration tab, click Disable WINS Resolution.
8.	On the Gateway tab, type 192.168.0.1 in the New gateway box, and then click Add.
9.	On the DNS Configuration tab, click Enable DNS, type the host computer name in the Host box. NOTE: The Domain box can be left blank, and note that the computer name is case-sensitive.
10.	In the DNS Server Search Order box, type the IP address for your HOST computer (usually 192.168.0.1),, and then click Add.NOTE: If the HOST IP address does not work properly, try using your ISP's DNS server IP address.
11.	Click OK, click OK again, and then click Yes if you are prompted to restart the computer.

For additional information about how to assign a static IP address, click the article number below to view the article in the Microsoft Knowledge Base:

230150 (http://support.microsoft.com/kb/230150/EN-US/) How to Configure a Permanent IP Address for Network Devices

The Host Connects to the Internet But the Client Does Not

With the Host connected to the Internet, test the LAN and Internet connections by performing the following procedures:

•	Use Winipcfg Tool To use the Winipcfg tool to verify the IP address, follow these steps: 1. Click Start, click Run, type winipcfg, and then click OK. 2. In the Ethernet Adapter Information box, select the network adapter. 3. Click Release, click Renew, and then click OK. If the IP address for the network adapter is 192.168.0.x (where x is a number between 2 and 254), the client successfully obtained an IP address from the host. If the client does not obtain an IP address from the Host, you may need to enable the DHCP service on the Host or manually assign a static IP address to the client.
•	Ping IP Address of Host To use the Ping command to verify the functionality of Transport Control Protocol/Internet Protocol (TCP/IP), follow these steps: 1. Click Start, point to Programs, and then click MS-DOS Prompt. 2. At the command prompt, type ping 192.168.0.1, and then press ENTER. 3. At the command prompt, type exit, and then press ENTER to return to Windows. If you receive a reply, the client computer is able to communicate with the Host computer over the LAN with TCP/IP. If you do not receive a reply, troubleshoot the issue as a general network connection problem in Windows. For information about troubleshooting network connection problems in Windows, click the article number below to view the article in the Microsoft Knowledge Base: 192534 (http://support.microsoft.com/kb/192534/EN-US/) Troubleshooting Windows 95/98 Network Connection Problems
•	Ping IP address on Internet To ping the IP address of a Web site on the Internet, you first need to obtain the IP address of a Web site on the Internet from the Host. To obtain the IP address for a Web site, follow these steps: 1. On the Host computer, click Start, point to Programs, and then click MS-DOS Prompt. 2. At the command prompt, type ping (where is the Uniform Resource Locator (URL) of a Web site), and then press ENTER.NOTE: Some Web sites (such as www.microsoft.com) may not return a reply, if this occurs, try a different Web site. 3. If the Web site returns a reply, you should receive the following message: pinging [xxx.xxx.xxx.xxx]... Where is the Uniform Resource Locator (URL) of the Web site and xxx.xxx.xxx.xxx is the IP address of the Web site. 4. Write down this IP address to use later. After you have obtained the IP address for a Internet Web site, to test the TCP/IP connection on the client, following these steps: 1. On the client computer, click Start, point to Programs, and then click MS-DOS Prompt. 2. At the command prompt, type ping xxx.xxx.xxx.xxx (where xxx.xxx.xxx.xxx is the IP address for the Internet Web site), and then press ENTER. 3. At the command prompt, type exit, and then press ENTER to return to Windows. If you receive a reply, the client computer is able to communicate with the Internet over the LAN with TCP/IP. If you do not receive a reply, refer the the Host Configuration section mentioned previously in this article for steps to configure and troubleshoot problems with the Host computer.
•	Ping Internet Name If the client can successfully ping the IP address of a website, use the Internet name to test the DNS configuration with ping. To do this, follow these steps: 1. Click Start, point to Programs, and then click MS-DOS Prompt. 2. At the command prompt, type ping (where is the Uniform Resource Locator (URL) of a Web site), and then press ENTER. NOTE: Some Web sites (such as www.microsoft.com) may not return a reply, if this occurs, try a different Web site. If you receive a reply, the Host and client computer are configured and working correctly. NOTE: If your browser is still unable to open a Web Site by name, check the browser's connection settings and make sure it is configured to use the LAN to connect and that no proxy servers are configured.
•	Open IP Address in Browser To test the browser by attempting to open a Web site by the IP address, follow these steps: 1. Click Start, click Run, type http://xxx.xxx.xxx.xxx (where xxx.xxx.xxx.xxx is the IP address of the Web site), and then click OK. If the Web site is displayed, the browser is functioning properly and there may be a problem with Domain Name Server (DNS) resolution. For additional information about configuring DNS, click the article number below to view the article in the Microsoft Knowledge Base: 229974 (http://support.microsoft.com/kb/229974/EN-US/) Connection Error Messages When You Use ICS with an FQDN If the Web site is not displayed, there may be a problem with Winsock on the computer. For information about possible Winsock issues, click the article number below to view the article in the Microsoft Knowledge Base: 188952 (http://support.microsoft.com/kb/188952/EN-US/) "Internal Error Occurred" Error Message Using Internet Explorer

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Damaged Registry Keys

This issue can occur if one or more registry key is damaged. To resolve this issue, follow these steps:

1.	In Network properties, write down the description of each of the protocols listed.
2.	In Registry Editor, open the following key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\NetTrans\nnnn Where nnnn is an incremental four-digit number starting at 0000.
3.	Check the number of subkeys under the NetTrans folder with the number of instances of protocols installed in the network configuration. There should be one subkey for each instance of a protocol installed. If there are more keys than protocols listed in Network properties, uninstall ICS, export a copy of the NetTrans key, and then delete the NetTrans key from the registry. This can remove all components from the network configuration except the adapters installed.
4.	To rebuild the NetTrans key, double-click Network in Control Panel, and then click the Add button on the Network Configuration tab. Click Client, click Add, click Client for Microsoft Networks, and then click OK. When the Network Configuration screen returns, it will have added the default protocol and rebuilt the NetTrans key in the registry so that there is only one subkey for each protocol installed.
5.	Check the registry again to make sure that only one NetTrans subkey exists per protocol installed. If so, reinstall ICS on the host and check to see if the problem is resolved.