Why is the internet (via ethernet) working on one pc but not on another or a mac?

December 22, 2011 7:52 PM

Internet works on one windows 7 laptop via ethernet but not on a macbook pro and not on another windows 7 laptop. Ethernet is my only option right now, router is not available. I want to fix this particular issue not internet connection sharing (thank you for thinking though).

Windows 7 laptop on which the internet works is a pretty clean and fresh computer running nothing but Microsoft security essentials and windows firewall (built-in).

The Windows 7 laptop #2 is running Comodo firewall (which was disabled) and has Microsoft security essentials installed.

The Mac has the mac firewall running (from security and privacy in system preferences which i also disabled) and little snitch. I believe both were disabled but still led to the same issue of it not working.

posted by iNfo.Pump to Computers & Internet (4 answers total)

Clarification question: how do you mean by "not working." Like... the OS complains that your ethernet cable isn't plugged in? It thinks it has Internet but you can't get anywhere? You can't get to only certain sites? etc.


I know it might seem like the long way around the horn, but one of my early steps is: go download a bootable live CD of some Linux flavor (I'd probably vote Ubuntu because they have a nice download and how-to-make-bootable-CD page) on the good laptop. Burn the CD, plug Ethernet cable into the "bad" laptop, boot it off the CD. Click the "just try out" option, not the "install" option and see if you can get anywhere with Firefox, etc.

That'll tell you if it's a hardware problem or a problem with Windows. (I'm slightly ignoring the Mac laptop because I don't know if the Mac hardware will be supported from the Ubuntu CD; but it might. One problem at a time.)

If booting from the CD works but booting from the Win7 on the hard drive doesn't, it's time for either rip-and-tear or a fresh install.
posted by introp at 8:14 PM on December 22, 2011

How are you connecting to the internet? You say "Ethernet is my only option right now, router is not available", does this mean you connect via a modem of some kind (DLS, cable, or dial-up)?
posted by RichardP at 8:22 PM on December 22, 2011 [1 favorite]

Are you just unplugging the ethernet cable from the working laptop and plugging it directly into each of the other devices in turn? If so, have you tried turning the modem off for a few minutes (minutes, not seconds) in between each swap so your ISP acknowledges and authorizes the connection of a new device? I remember having to do that years ago when routers were less common.
posted by bcwinters at 9:01 PM on December 22, 2011 [2 favorites]

One possible issue is MAC filtering. The MAC is unique* for all network interfaces. This may lead you down the right path... at least it's something to keep in mind.

- MAC collisions do happen, though they are rare.
posted by PROD_TPSL at 10:32 PM on December 26, 2011