What Is Internet Connection Sharing?

Internet Connection Sharing, or ICS, is a built-in feature of Windows computers (Windows 98, 2000, Me, and Vista) that allows multiple computers to connect to the Internet using one single Internet connection on one computer. It's a type of local area network (LAN) that uses a single computer as the gateway (or host) through which other devices connect to the Internet. Computers wired to the gateway computer or connecting to it wirelessly via an ad-hoc wireless network can use ICS.

Some of the features of Internet Connection Sharing include:

Allowing most any kind of device (including non-Windows and older Windows systems) to connect without having to install additional client software.Support for all of the connected clients to use many different protocols, including VPN and Internet gaming.Clients are automatically given an IP address and configured for DNS through the ICS computer.

In Windows 98 or Windows Me, ICS needed to be enabled or installed on the host computer from the Control Panel Add/Remove Programs (on the Windows Setup tab, double-click on Internet Tools, then select Internet Connection Sharing). Windows XP, Vista, and Windows 7 have this built-in already (look in the Local Area Connection properties for a setting under the Sharing tab to "Allow other network users to connect through this computer's internet connection").

Note: ICS requires the host computer to have a wired connection to a modem (e.g., DSL or cable modem) or an aircard or other mobile data modem, and the client computers either wired to your host computer or connecting to it via the host computer's free wireless adapter.

Learn how to use Internet Connection Sharing:

Examples: To share one Internet connection among several computers you can either use a router or, on Windows, enable Internet Connection Sharing so that other computers connect to one computer that has an Internet connection.

Your Laptop's Connection Can Help Your Phone...

There are many different situations where you might want to connect your laptop and mobile device to share Internet access. Most traditional tethering cases involve using a cell phone as a modem to get a laptop or tablet online, but sometimes we might want to do the reverse--use our laptop's data connection for Internet access on our Android phone or iPhone, tablet, or other mobile device. You can accomplish this "reverse tethering" from your Windows PC or Mac to your Android or iPhone device in a couple of ways.

You might be thinking what's the point, since mobile phones have 3G/4G data built in and should be able to go online on their own.

Sometimes that data access isn't available, though, or we're trying to conserve our mobile data access (e.g., avoid data roaming charges when traveling or overage fees on tiered or prepaid data plans). For example, sharing your laptop's Internet may make sense when:

You want a more secure Internet connection than Wi-Fi on your mobile phone or tablet but don't have access to 3G or 4G. (Public Wi-Fi isn't secure at all.)Working in an office where only laptop Wi-Fi connections or Ethernet connections are allowed and mobile phone usage is blockedNeed Internet access faster over Wi-Fi than on 3G/4GYou're traveling and the hotel only gives you a single wired Ethernet Internet connection

You can share the laptop's data connection over Wi-Fi or over a wire, depending on your setup. (If you share your laptop's connection over Wi-Fi, you're essentially turning your laptop into a Wi-Fi hotspot for all who know the security code to use.) Here are a few options:

Windows: Use Internet Connection Sharing (ICS): Internet Connection Sharing or ICS is built into Windows computers from Windows 98 to above. An example of Internet Connection Sharing is if you have a laptop connected via wire to a router or modem and then share that connection to a phone or tablet either over the Wi-Fi adapter or through another Ethernet port. Here are instructions for setting that up on XP, on Windows vista, and on Windows 7.

Mac: Use Internet Sharing: Mac OS X also has its own version of Internet Sharing built-in. Basically, you share your wired Internet connection or 3G connection with other computers, smartphones, or tablets--who connect to the laptop over Wi-Fi or Ethernet. Follow these instructions to share your Mac's Internet Connection.

Windows 7: Use Connectify (Preferred): The methods above essentially bridge your connection from one type of Internet connection (e.g., wired modem) to another (e.g., Wi-Fi adapter). You can't use the same Wi-Fi adapter to share the Internet access--unless you use a third-party tool.

Connectify is free software that shares a single Wi-Fi connection over Wi-Fi--no need for a second adapter or for your laptop to be wired to the Internet. It's only available for Windows 7 and above, however. One of the main advantages of Connectify over the above methods is that the connection is more secure--using WPA2 encryption in Access Point Mode versus the very insecure WEP, as the ad hoc networking modes above do. See these instructions for turning your Windowsx laptop into a Wi-Fi hotspot for your phone and other devices.

Windows/Android: Use Reverse Tether App for Android: Reverse Tether is a trialware (limited trial, $4.99 for full version) dedicated to just this reverse tethering purpose. You can connect your mobile device to the Internet on your laptop with one click over a USB connection. This is more secure than using the Wi-Fi ad hoc connection, but the app may not work for all Android phones or devices.

I haven't seen anything like this yet for iPhone users, but there may be a few apps available if you have a jailbroken iPhone.

If the network settings don't work for you, you don't want to use third-party software, or you want something with more features, an inexpensive alternative is buying a travel router. With a wireless travel router, you can share a single wired, wireless, or mobile data connection with multiple devices. As the name implies, these devices are pocketable.

See: Top 7 Travel Wireless Routers for a selection.