Your computers might not be able to connect to each other unless your wireless router stays out of their way.
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Adding a wireless router to a wired network? Here's how to keep it from blocking access to your other home computers

Oct. 22, 2006

By Al Fasoldt
Copyright © 2006, Al Fasoldt
Copyright © 2006, The Post-Standard

   Nearly all the newest laptop computers come with wireless capabilities built in. That means you can do your e-mail and surf the Web right from your easy chair if you install a wireless router at home.
   It's easy, except for one little thing. (There's always "one little thing," right?) Unless you configure your wireless router in a special way, you won't be able to connect to your desktop computer from your laptop. Likewise, your desktop system won't have a clue that your laptop is nearby.
   In other words, computers in your own home might not be able to connect to each other unless your wireless router stays out of their way.
   Let me explain. If you have a broadband connection such as cable or DSL, the typical way of connecting multiple computers to the single Internet connection is through a cable or DSL router. The router, a small box with a bunch of cable jacks and LEDs, assigns network IP (Internet Protocol) addresses to all the computers connected to it.
   So if you already have a home network -- consisting of the family computer plus one used by the kids, for example -- they get onto the Internet through a router. If you have more than one router, the one that supplies the Internet connection to all your home computers is called the primary router. (Tech note: If you have only one router, it's still called the primary router. No sense hurting its feelings.)
   It's when you add that second router, the wireless one, that you encounter that "one little thing." Because it's a router, the first thing it wants to do is create a route for data. But the only way it knows how to do that is to assign an IP address to all the computers it finds on the network.
   Uh-oh. Bad little router. It doesn't check first to see if those computers already have an IP address. So it tries to give them another one, using what's called automatic addressing.
   But just as I can't be both Al and Jim, a computer can't be both 001 and 002. The computers get confused, just as I would if half my friends started calling me Jim.
   And, of course, nobody on the network answers to the right name any more once their names -- their addresses -- get changed on the fly like that.
   The fix is simple. You tell your wireless router to leave network addresses alone. In other words, you turn off automatic addressing in your wireless router.
   There are many brands of wireless routers and they handle this in different ways. In Apple's Airport routers using the current Airport software, the setting is in the Network tab; turn off (uncheck) "Distribute IP addresses" and click the "Update" button. You'll find similar settings in all other wireless routers. You want to turn off, uncheck, disable or undo any setting that assigns, sets, distributes or manages IP addresses. (Yes, all those terms are used, in one way or another. Nerds have a tough life.)
   After this change, your computers should be able to see each other on your home network. Your job's not quite done, however, because you probably don't want anyone out on the sidewalk to be buddy-buddy with your computers, too. We'll take a look at wireless security in a couple of weeks.