My friend has a D-link router. His daughter got a Sony laptop with Vista home premium. The computer was able to connect to the router. We decided to add MAC filtering so we added the MAC address of the wireless card and the wired card. The computer cannot connect wirelessly when we switch on the MAC filtering. When we hook up the wired card, it then works fine.
My question is, is this a known problem with Vista or the Sony wireless card? Does MAC filtering also apply to wired cards (if I remember it does)?
Nope. It's a know problem with users that don't supply numbers with their questions. What model number DLink and what model number Sony laptop?
The usual problem is that the wrong MAC address is used for the laptop wireless. Each network "interface" on the laptop has a slightly different MAC address.
On the Sony laptop with the Vista nightmare, do this: Start -> Run -> cmd ipconfig /all | more You should get a list of "interfaces", each with a corresponding MAC address.
To be fair to Jeff, you started with a long description of a specific problem which you clearly want to solve. It might be easier to accept Jeff's help in solving it, given that he is an acknowledged expert in this field.
If I myself were to answer the general question I'd say there's a problem with Vista in that its totally crap, and the best fix for your problem is to complain to your vendor till you get an XP install disk. However I suspect this idea will just annoy some people :-)
MAC filtering in many routers covers the wireless connections only. But given how trivially simple it is to defeat, MAC filtering often ends up being more trouble than it's worth. As you've discovered.
Yet given the hundreds of model variations possible, it IS important to give model number info.
But here's a better suggestion, use the CMD prompt and do an 'ipconfig /all' on the machine that's not connecting and post the FULL text of what it says.
There were several (I think around 4) but the two that I used were labeled in such a way that I knew which one was for the wired network card and which one was for the wireless network card. I used the ipconfig /all command and that gave a description of the card that the MAC address belonged to, either company name or a good enough description.
Why is it easier to defeat? How do other people know what MAC addresses I have given permission to? Do they sniff the signals from wireless cards and determine the MAC addresses of those that are accepted?
Because it's easy to spoof a MAC address. For example:
Yes, by sniffing. MAC addresses are NOT encrypted and are easily sniffed.
However, the real problem with MAC filtering is the maintenance overhead. Typically, I would setup a customers system with MAC filtering for their various computahs. A while later, a visitor shows up and wants to connect to the internet via wireless. They give him the WPA password, but nothing works. I then get a phone call (usually at some inconvenient time) asking for a fix. Of course, since the visitor is now irate, it's deemed a crisis. Drop everything, login to the router (assuming I remembered to setup DDNS), and add the MAC address. I then get to wait a few weeks or months for it to happen again. Lots of variations on the same theme. The basic problem is that unlike the WPA password, you can't just issue a free ticket to use the wireless. It requires diving into the config and manually adding the MAC address. At this time, none of my customers use MAC filtering. WPA (or RADIUS) is good enough.
Incidentally, most wireless AP's and router are stupid in handling MAC address filtering. Instead of allowing a user to import a text file with a list of acceptable MAC addresses, the user is expected to type in each MAC address, one at a time. I have about 30 machines that might need to connect. What do you think the chances are of typing them perfectly?
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