How can I properly set up my home network?
November 24, 2010 7:03 AM   Subscribe

How can I properly set up an internet connection on both a laptop (wireless) and desktop using DSL? Getting IP address conflict! GRR.

I have a linksys wireless router, a desktop (Win7), a laptop (Win XP Pro) and DSL. Here is what I've done and the results:

1. Tried to connect the router as if there was no desktop (DHCP enabled, internet plug from modem into internet slot on the router). Cannot get a hardwired or wireless connection. This worked days ago on a cable connection.

2. Was told by a tech guy that because of the DSL I need to disable the DHCP on the router and rearrange the plugs: internet plug into slot #1. The laptop picks up both wired and wireless connection. First thing solved.

3. When I plug the desktop into slot #2 on the router I get an IP conflict on both computers and neither get a connection. I am completely lost now.

I have been searching high and low for a solid set of instructions but there is so much crap out there I am having an issue narrowing down my problem. Odd because I would think this is a common setup.

Can someone point me to instructions that apply to this situation? Or even help?
posted by Snackpants to Computers & Internet (7 answers total) 4 users marked this as a favorite
How is your Internet connection SUPPOSED to work? Do you just get an IP address via DHCP and that's it or do you have to dial up? If you need to dial (PPTP or PPPoe), the solution that the tech person gave you is correct if suboptimal - that way, you're using your fancy router as a wireless access point, and only one computer at a time can dial into the network.

What you actually WANT to do is to put the Internet back on the port it belongs and teach your router to do this dialup procedure in its configuration.
posted by themel at 7:19 AM on November 24, 2010

You need to make sure your desktop doesn't have a static IP address assigned to it, from the sound of it.

Unplug everything, plug it all back together, one thing at a time.

Make sure that:

- all three devices are set up to use DHCP - that is, they get their addresses automatically, and there's no numbers in the boxes that say IP address, netmask, gateway, all that.
- the desktops are wired into the numbered ports on the Linksys router
- the Linksys router is connected, at the port labelled "internet", to the DSL box, and
- that the DHCP bits are enabled on the router.

... and it should just work.

The tech guy was... misinformed, to put it politely. What that Linksys box is doing for you is two things, bascially - DHCP and NAT. DHCP means "will give computers that ask an IP address", and NAT means "will forward traffic from those addresses on to the internets."

The reason that the "internet" port is important is because that port isn't giving out IP addresses to stuff plugged into it - it's asking your DSL modem (well, it's asking something well upstream of it, really, but for the sake of argument play along) for an IP address of its own, so that it can route traffic from your home computers out to the intertubes.
posted by mhoye at 7:23 AM on November 24, 2010 [1 favorite]

Does your DSL provider require a program to be installed on one (or both) of your computers that "logs into" and starts up the DSL connection? Many DSL providers use PPoE so that when the connection is not being used, it gets turned off. Then when you "log in" it gets reactivated.

Your router likely has a section in it's control panel where you can put in your DSL log in credentials.

What kind of router (brand and model) do you have? Who is your DSL provider?
posted by reddot at 7:23 AM on November 24, 2010

mhoye and reddot have it. Here are some basic instructions to help you along.

To answer question 2), many DSL techs are told not to assist with routers as the DSL companies can charge you for additional IP addresses.
posted by anti social order at 8:07 AM on November 24, 2010

What I would do is factory reset your linksys, make sure all of your computers are set to use DHCP and call the DSL provider back and talk to a tech that knows what they are talking about. If he tells you to disable DHCP on your router, then something is wrong.
posted by empath at 8:29 AM on November 24, 2010

Best answer: First thing is to put the router aside, and make sure you can get an Internet connection with the DSL modem connected directly to one of your computers. If your ISP supplied the DSL modem, they might have given you a setup CD-ROM to make it go. Personally I prefer to ignore those and do the required setup by hand; I don't trust ISPs (especially big ones) not to try to crap up my computer with bloatware.

So as a preliminary step, disconnect the modem from the phone line, wire a computer's Ethernet port to the modem's LAN port, switch everything on, and check the properties of the Ethernet connection on the computer side.

Most DSL modems are actually also configured as NAT routers by default. If yours is like that, you will get a functioning connection between modem and computer even without the Ethernet connected, and your computer will be allocated a private-range IP address (typically 192.168.x.x or 10.x.x.x). The modem itself will also get an IP address in that same range.

On Windows, you can find the computer and modem IP addresses by opening a cmd window (do this using "run as administrator" if on Windows 7), typing ROUTE PRINT at the prompt and pressing Enter. On the line where Network Destination is and Netmask is, the Gateway value will be the modem's IP address and the Interface value will be the computer's IP address.

If both those addresses are in fact in the same 192.168.x.x or 10.x.x.x range, it's now time to fire up a web browser and type the modem's IP address into the address bar to open the modem's setup pages. Some modems will want you to supply a username and password before letting you in; Google "default password" and your modem's model number ahead of time to find out what to use.

Poke about in the modem's setup pages until you find the right place to set up the WAN connection and enter stuff like your ISP-supplied username and password, VPI and VCI numbers and whatnot (visit your ISP's support site ahead of time and write down the configuration details). Once that's done (which may involve a modem reboot, depending on model) plug in the phone line, wait for the modem to get DSL sync, and then make sure it can log on to your ISP and you can surf the web.

Next thing is to set up the modem's DHCP server to find out or set up what address ranges it will hand out over DHCP. Some modems are set up to hand out any address in their subnet except their own: for example, if the modem is on, it might be set up to hand out anything from to via DHCP. That's excessive; for a home LAN, at most 100 available DHCP addresses are plenty. If you can, configure it to hand out a restricted range from say to Just make sure the modem's own address, and a handful of others nearby, are outside the DHCP-available range.

Now turn your attention to the wireless router. By default, it will also be set up to do NAT between its LAN (including wireless) and WAN (Internet) ports. If your DSL modem is in fact a router as I've been assuming, you don't want it doing that; double NAT makes things slower and more complicated than they need to be.

So disconnect your computer from the DSL modem and plug it into one of the router's LAN ports. Do the ROUTE PRINT dance again and get into the router's config web page. See if you can find a way to disable NAT, which will effectively make the router treat its WAN port as just another LAN port.

Next, give the router a static IP address adjacent to the DSL modem's. For example, if the modem was on, set the router up at; if the modem was on, make the router The netmask for a consumer-grade router will almost always be Use the DSL modem's IP address as the default gateway. This step will almost always need a router reboot to become effective.

Nearly done now. Since the router won't be doing NAT, and is instead going to be inside the same subnet as the DSL modem, you don't want its DHCP server competing wih the modem's. Browse to the router's config page again at the newly set IP address, and disable its DHCP server (your computer will already have picked up an address from it, and that will stick around until you unplug the Ethernet cable).

Moment of truth: unplug all the Ethernet cables, then connect one between the DSL modem's LAN port and the router's WAN port (if you did manage to disable NAT in the router) or one of its LAN ports (if you didn't). Then wire your computer to one of the router's LAN ports.

If you do another ROUTE PRINT, you should see that the DSL modem is once more the default gateway, and that your computer has been given an IP address from the range you told the DSL modem's DHCP server to use. And you should now be able to browse to any Internet site you like, and the router's config page, and the DSL modem's config page.

Plug in (or connect wirelessly) a second computer, and it should get another address from the DHCP pool and should also be able to do all the things your first computer can. You should not at this point be seeing any IP address conflicts.

Now, if your DSL modem is not in fact a NAT router in its own right, a different set of setup steps will be required. But you can post back for those; it's past my bedtime.
posted by flabdablet at 8:38 AM on November 24, 2010

Gah. For

If yours is like that, you will get a functioning connection between modem and computer even without the Ethernet connected


If yours is like that, you will get a functioning connection between modem and computer even without the Internet connected.
posted by flabdablet at 8:40 AM on November 24, 2010

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