HELP! iMac, cable modem won't go.

[NTLVictim]

Regarding Mr Fibre (English spelling ):

What he said.

Interesting question about the SACM being added after the STB, Id like to hear the answer to that one, it could explain a lot!

[melevittfl]

Originally Posted by Dark Fiber

Now, although a connected computer's operating system can be "hacked" to cause IP packets originated by the machine to contain a "soft" MAC number instead of the Media Access Controller's "hard" MAC number, it doesn't necessarily follow that its Media Access Controller will respond to incoming interrogations with packets containing the "soft" MAC number

Yes, it does. The MAC Id is an address, just like an IP address. The ifconfig command simply tells the hardware to use one address vs. another. It doesn't get confused over which one its supposed to use.

Originally Posted by Dark Fiber

(because Media Access Controllers are designed to be largely autonomous so as to "take the load off the CPU". This is why ethernet connections are vastly superior to USB connections in the context of networking.)

You're mixing up Media Access Controller with Media Access Control Addresses. What you're describing are special ethernet chips that do some of the calculations required for TCP/IP networking that would normally have to be done by the CPU. The MAC address is simply an address, just like an IP address.

Originally Posted by Dark Fiber

A home gateway router is, however, rather different. Its Media Access Controller is specifically designed to be "programmable" to take account of those ISPs who try to restrict access to a single computer by reference to its MAC number. If cloned with a client machine MAC number, a home gateway router _must_ respond to interrogation with packets containing the new MAC number and indeed use that MAC number under all circumstances.

Not really. A home router is pretty much the same as a computer except it uses flash ram instead of a hard-disk. Most of them run Linux (a Unix variant just like Mac OS X). Setting a router to use a cloned MAC address is exactly the same as the ifconfig command. Its software would write a configuration file to the flash ram to make sure that the setting stayed when the router was reset, but you could do that on the iMac as well. It's just software.

Now, that being said, I think having Striper change the MAC address is not a permanent solution either, but it would let him go back to NTL and know it's a problem with their end.

And you're also right that if the router turns up and it works when cloned to the old G3's Mac address, than he may be best off simply accepting that and use the router.

[NTLVictim]

Routers are also handy for moving stuff and doing backups when you have more than one PC.

[stripes]

Hallo gang.

It's the router wot won it.

Router set up, after a bit of fiddling (and Dark, wouldn't go unless I hit the CLONE MAC button on the Belkin set-up page), et voila, www access on G3 and iMac.

Now, apart from INCREDIBLE relief (I gave up drinking 5 years ago, but have been sorely tempted in the past weeks), some points.

1. CAN I TURN THE G3 OFF or I am stuck with the machine forever? I shall try disconnecting it a bit later, but I am suspicious.

2. WHAT DOES THIS ALL PROVE (except that you are a great bunch of people, and I am glad you are there)? What does it prove in terms of me having a pop at NTL - if nothing else, to enable me to get my G3 off my desk and down to Oxfam.

3. WWW. It's not about downloading pretty piccies or tunes, it's about this, the exchange of knowledge and information, and as such, utterly invaluable.

4. Didn't try the new form of the sudo string, Mark, as the Router arrived first. And hospital says my blind eye will 'probably' get better. (Probably?)

5. STB has been there for years, and G3 working on ntl broadband alongside the tele, no previous problems.

6. Dark. Thanks a million for your input, particularly getting up in the middle of the night, to boot. No, my choice of words over the 'legal' business was wrong. I meant 'legitimate' in the broader sense, i.e. I would never buy something as complicated as a Mac from the likes of PC World. Ink cartridges, maybe.

So, I sit here smugly, two computer screens on and glowing, waiting for your comments (as usual!)


A happier Allen.

[NTLVictim]

Yeeeeeeeeeeeeessssssssssssssssssssssss............ .

---------- Post added at 10:06 ---------- Previous post was at 09:57 ----------

May I just take this moment to point out our "add to reputation" buttons on the bottom left of our name boxes? It's next to the little triangle.....

Cough...

---------- Post added at 10:37 ---------- Previous post was at 10:06 ----------

Now I've finished jumping about, the router thinks its the G3, so yes, you can do with it what you will, although I'd keep it for data backup etc...

Please make a note of the MAC address if you dispose of it, just in case you need to put the details back into the router, if you upgrade or whatever.

[stripes]

Hello NTLVictim.

Replying on the iMac. Ain't half quieter.

Well, so far I've turned the G3 off, just (taking screen shots of TCP IP panels etc first for printing out and keeping so I've got the data). Later I'll try pulling the plugs...

I know it's Saturday, but could you have a look at my no.2 question above, i.e. what does it prove? I am not really bothered about having a pop at ntl, it will only arise if I can't disconnect my G3 from the now growing circuitry.

Cheers.

Allen.

[NTLVictim]

Number 2 is what VM customer services are for fobbing you off...

Oh, question number 2..

It means that NTL/VM ARE blocking access to everything except the G3 via the MAC address, despite their claims that they ain't.

[Dark Fiber]

Originally Posted by stripes

I know it's Saturday, but could you have a look at my no.2 question above, i.e. what does it prove? I am not really bothered about having a pop at ntl, it will only arise if I can't disconnect my G3 from the now growing circuitry.

Cheers.

Allen.

In my opinion, the fact that the router didn't work until you cloned the G3 address into it strongly implies (but doesn't prove) that all the problems have been down to VM/ntl because now you've been unable to connect three computers (2 iMacs and the router) when it should have been straightforward.

melevittfl - I don't accept any of your points and my post was as long as it was because I was continually pasteing "Media Access Controller" when I meant hardware and "MAC address" when I meant data .
In short, even if a machine is set up for "spoofing", I don't see how you can rule out responses (that wouldn't involve the OS software) to ISP interrogation with the "hard" MAC address unless the computer's MAC hardware has some writable registers which for normal use it wouldn't need. Conversely, a gateway router has a Media Access Controller where those registers are able, by design, to be written to. Before cloning, my Belkin router had the same MAC address facing the WAN as facing the LAN- and that's against the rules
BTW I'm not claiming to be right, just logical! I would like to hear from any networking guru and any Mac hardware guru about my points.

[NTLVictim]

Dark, I reckon it proves it..I used to do this stuff for a living, God help me.

Anyway, we won!

[melevittfl]

Originally Posted by stripes

I know it's Saturday, but could you have a look at my no.2 question above, i.e. what does it prove? I am not really bothered about having a pop at ntl, it will only arise if I can't disconnect my G3 from the now growing circuitry.

It means that there system, for some reason, is only willing to give an IP address to a device that matches the MAC address of the original machine (the G3).

Make sure that you write down that MAC address in case you ever need to enter it into the router again.

Other than that, you won't need the G3 anymore. The NTL system things your router is the G3 and will assign an address to it. The iMac gets its IP address from the router and the router, as you might guess, routes the data between the iMac and the NTL network.

Glad you've got it working. And, let me say it was a pleasure helping you out. You had an interesting problem and you were very clear about what you'd tried and what the results were.

Good luck,
Mark

---------- Post added at 20:14 ---------- Previous post was at 19:50 ----------

Originally Posted by Dark Fiber

melevittfl - I don't accept any of your points...

OK. Don't know what I can say if this is your stance, but I'll try...

Originally Posted by Dark Fiber

In short, even if a machine is set up for "spoofing", I don't see how you can rule out responses (that wouldn't involve the OS software) to ISP interrogation with the "hard" MAC address unless the computer's MAC hardware has some writable registers which for normal use it wouldn't need.

Well, the computer's hardware does have "writable registers." The physical hardware has a bit of programmable data storage that holds configuration data.

The OS is capable of changing the configuration of the ethernet controller by changing the configuration data. The ability to change the MAC address uses exactly the same mechanism as setting the ethernet controller to full or half duplex and telling it to auto-negotiate the link speed or setting a specific one. It's stored in a re-writable EEPROM that's part of the ethernet controller.

If you don't believe me, there's Wikipedia:

From http://en.wikipedia.org/wiki/MAC_address
"A locally administered address is assigned to a device by a network administrator, overriding the burned-in address."

Originally Posted by Dark Fiber

I would like to hear from any networking guru and any Mac hardware guru about my points.

You mean, other than me?



Cheers,
Mark

[Dark Fiber]

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?

[NTLVictim]

[stripes]

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.

[melevittfl]

Originally Posted by Dark Fiber

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.

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.

Originally Posted by Dark Fiber

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?

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.

[Dark Fiber]

Originally Posted by stripes

Just an afterthought, gang.

I shall be contacting Apple ... 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, ..., we didn't actually FIX the problem, did we? ... 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.

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