Why won't my laptop connect to the internet?
August 8, 2010 2:01 PM   Subscribe

Why won't my laptop connect to the internet?

I have cable internet through Comcast. Most of the time, I have my cable modem plugged directly into my Mac, which works fine. (No router.)

I have a laptop running Windows XP that I need to temporarily connect to the internet so that I can update some software. I've probably not used this laptop in eight months. Previously, it did connect to the internet fine, but that was a DSL connection through another company in another state.

I tried just switching the cable from my Mac to my laptop, but after a long time "acquiring network address," it says it's connected but that the connection has "limited or no connectivity." Repairing the connection just stalls.

My experience with Comcast is that if I try to call for help, the person on the phone will have no idea what's going on, and will offer to send a technician over. That's totally unnecessary and I don't want to deal with it.

What can I do? (Other than try to pirate someone's wireless--no one around me has an unsecured connection! And I'm not familiar with what locations in my new town offer free WiFi.)
posted by Kutsuwamushi to Computers & Internet (8 answers total)
Best answer: Reboot the cable modem, and then reconnect your laptop. My experience is that whenever you change machines or routers plugged into a Comcast cable modem, a reboot of the modem is required to get it to work. Just unplug it, count to ten, and plug it back in. Then plug your PC back in, and you should be good. It has to do with the MAC address (just for clarity's sake, MAC =Media Access Control, which has nothing to do with Macintosh) of the Ethernet interface changing.
posted by deadmessenger at 2:04 PM on August 8, 2010

Yeah, reboot the cable modem. Nothing else should be required.

The longer term solution if you want to use both in a convenient way is a router, possibly with wireless.
posted by wierdo at 2:14 PM on August 8, 2010

Is your mac set up to use DHCP to acquire its internet address, or is it statically configured? It's most likely the former, but if it's the latter you need to set your windows machine to have the same static IP your mac is configured for.

I don't use macs so I don't know exactly the procedure for determining this, but my googling suggests you should choose "System Preferences" from the apple menu, then "Network" in the resulting dialog/menu, then pick the built-in ethernet connection (or whichever is more appropriate for your machine) from the "Show" menu, then click on "TCP/IP." There will be a drop-down labeled "Configure IPv4" -- if it says "Using DHCP" then your mac is acquiring an IP automatically from the router; otherwise, it's statically configured as a particular dotted quad (e.g.,

To configure your windows IP, select Start -> Control Panel, pick "Network Connections" then right click on the connection in question (usually labeled "Local Area Connection") and choose Properties. Scroll down to and select "Internet Protocol (TCP/IP)", click the Properties button, then instead of "Obtain IP address automatically" opt for "Use the following IP address" and copy the values from your mac. You will also need to do the corresponding bit for the DNS server, below.
posted by axiom at 2:19 PM on August 8, 2010

As above, some combination of one or all of the following tends to do it:

1) reboot/unplug cable modem
2) reboot/unplug router
3) Use Windows' "Repair" function on your Wireless connection (available by right-clicking network icon). Or if you prefer, open a command prompt and do ipconfig -release followed by ipconfig -renew.
posted by drjimmy11 at 2:24 PM on August 8, 2010

do ipconfig -release followed by ipconfig -renew

That should actually be ipconfig /release followed by ipconfig /renew. Dashes won't work.
posted by axiom at 2:31 PM on August 8, 2010

Are you able to get working internet on another device? When I recently had this problem, I investigated and found out that my roommate hadn't paid the bill in 5 months and Comcast had shut us off.
posted by phunniemee at 2:44 PM on August 8, 2010

Best answer: Alternatively (if you have wifi cards in both the laptop & iMac): just keep the iMac connected and share it's Internet connection over wireless (look in System Prefs on OS X).
posted by dirm at 4:08 PM on August 8, 2010

Some systems actually keep track of the MAC address of the device that is supposed to be plugged into the connection...as others said if you do a "release/renew" for DHCP address it probably will work. If you do buy a router make sure it supports the clone MAC address feature so you can put in the MAC address of the original computer that Comcast connected the modem to.
posted by white_devil at 9:17 PM on August 8, 2010

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