Re: HELP! iMac, cable modem won't go.
 

Mark,
<Grovel Mode ON/ It may amuse you to know (or it may annoy you intensely!) that my speculations were based on a mistake. I wrongly thought that Stripes had _successfully_ spoofed the G3 MAC address into his iMac and that this had _not_ permitted connection to the cable network. I was confident that using a gateway router cloned to the G3 MAC address would work. Consequently, I was casting about for ways to resolve the apparent paradox. Hence my ideas that the MAC in a spoofed computer might return the hard MAC address if the MAC acted autonomously in response to the ISP probe. /Grovel Mode OFF>

Thank you for the Wiki info, it will take some time to assimilate. I note that the Wiki includes the phrase "if the service provider is able to detect that a MAC address is spoofed". How would this be achieved if the spoofed hardware is truly _identical_ in its responses to unaltered hardware? Do you, in fact, believe that the MACs in home gateway routers are identical with those installed in computers?

Re: HELP! iMac, cable modem won't go.
 

:D

Re: HELP! iMac, cable modem won't go.
 

Just an afterthought, gang.

I shall be contacting Apple to do my own grovelling, (after all, thanks to me/ntl they took back a perfectly good brand new iMac!) but also to suggest that they set up some communication with the broadband cable suppliers, so that in future situations like this, they can phone direct and try and sort out the problems, rather than doing the conventional thing (very un-Apple) and relying on their customers to become piggy in the middle.

After all, although I'm certainly up and running and all the help you've given has preserved my sanity through this lot, we didn't actually FIX the problem, did we? (Viz: this morning I plugged my iMac into the modem, bypassing the router, and, of course, I wasn't connected to the internet. So, if my router blows up next month, I'll be almost back to square one (at least till I can buy a new router!)).

Allen.

Re: HELP! iMac, cable modem won't go.
 

Ahh. Yes, I can see how that would lead you down that line of thinking. No worries. I hope I didn't come across badly in my reply.

Yes, the ISP could detect a cloned address, but it's nothing to do with the hardware. One possible way is simply by seeing if the data "makes sense". If you notice, the default, or "burned in" address starts with a sequence that is unique to a particular manufacturer. So, Belkin routers will have a MAC address that starts with XX:XX:XX (for example), and Apple computers will have a MAC address that starts with YY:YY:YY.

Now, the TCP/IP stack (the bit of code that implements the TCP/IP protocol) of an operating system has characteristics that usually allow it to be identified. That is, by simply connecting to a networked device, it is often possible to determine which operating system it is running. If you search for a program called NMAP, you'll find an example of a program that does just that.

So, lets take Stripes' situation. NTL can look at the (now cloned) MAC address and determine that it was assigned to Apple. However, if they scan the machine, they will see that it's not running Apple's OS X, but rather an embedded OS (Linux perhaps). This gives them a clue that the MAC address has been cloned.

There are other ways, but they generally rely on the same kinds of things, rather than on any difference in the address itself.

As you can see, it's not a foolproof process and it takes a bit of detective work, so I doubt most ISPs bother.

Re: HELP! iMac, cable modem won't go.
 

1) Good luck with Apple UK, I'm afraid that they would take the view that this was such an oddity that an Apple/VirginMedia hotline would not be cost effective.

2) No, it's up to VM/ntl to put this right for your connection. Again, I doubt that a frontal attack would be any use. However, there are lurkers here at CF with hotlines to VM/ntl and it would be interesting to see if they could achieve anything or if it's just a coat of red paint ;)

Mark, your unworthy student bears the marks of his guru's whip upon his back with pride :D

Re: HELP! iMac, cable modem won't go.
 

Attention ntl/virginontheridiculous CS/ Tech support...

We won, you were crap.

This is our world, you just live in it.