Do MAC addresses go to internet?

Or, the frame headers are peeled off by the router, so only layer 3
packets go to internet?
In other words, The sender's MAC is hidden from the internet
reciever(or sniffers in the route).

Which story is true?

Thanx

On Sun, 21 Oct 2007 09:45:46 -0700, (E-Mail Removed) wrote:

> Or, the frame headers are peeled off by the router, so only layer 3
> packets go to internet?
> In other words, The sender's MAC is hidden from the internet reciever(or
> sniffers in the route).
>
> Which story is true?

#2

On Oct 21, 12:53 pm, Dave Uhring <daveuhr...@yahoo.com> wrote:
> On Sun, 21 Oct 2007 09:45:46 -0700, sakradevanamin...@gmail.com wrote:
> > Or, the frame headers are peeled off by the router, so only layer 3
> > packets go to internet?
> > In other words, The sender's MAC is hidden from the internet reciever(or
> > sniffers in the route).
>
> > Which story is true?
>
> #2

But ISPs know MACs, well that's what I heard, not sure if its true.

say I have a linux router, there are 3 pcs behind it and having
internet acess. ISP knows these 3 MACs, that's okay. But if I host a
hundred PCs behind the router, then the ISP may be unhappy because
they know there are 100 different MAC addresses sharing one public IP.

(E-Mail Removed) wrote:
> On Oct 21, 12:53 pm, Dave Uhring <daveuhr...@yahoo.com> wrote:
>> On Sun, 21 Oct 2007 09:45:46 -0700, sakradevanamin...@gmail.com wrote:
>>> Or, the frame headers are peeled off by the router, so only layer 3
>>> packets go to internet?
>>> In other words, The sender's MAC is hidden from the internet reciever(or
>>> sniffers in the route).
>>> Which story is true?
>> #2
>
> But ISPs know MACs, well that's what I heard, not sure if its true.
>
> say I have a linux router, there are 3 pcs behind it and having
> internet acess. ISP knows these 3 MACs, that's okay. But if I host a
> hundred PCs behind the router, then the ISP may be unhappy because
> they know there are 100 different MAC addresses sharing one public IP.
>
I guess what matters to ISPs is bandwidth. Is not it? So as long as you
are sharing the bandwidth among the computers behind the router, these
should all be fine but I wonder how are you using same public IP for all
the computers?

They cannot share the same (public) IP when they are in LAN, probably
you might be using some private ip-range for them but proxying the
internet network through the router. Could you Confirm?

Thanks, Nikhil

On Sun, 21 Oct 2007 11:38:32 -0700, (E-Mail Removed) wrote:

> But ISPs know MACs, well that's what I heard, not sure if its true.

You can hear many things.

> say I have a linux router, there are 3 pcs behind it and having internet
> acess. ISP knows these 3 MACs, that's okay.

What makes you believe that?

Can *you* see any MACs other than that of your ISP's device?

Oh, shit! Here I am trying to make sense to a googlegrouper.

On 2007-10-21, (E-Mail Removed) <(E-Mail Removed)> wrote:
>
> But ISPs know MACs, well that's what I heard, not sure if its true.

Depending on their and your network architecture, they may or may not
know your MACs.

> say I have a linux router, there are 3 pcs behind it and having
> internet acess. ISP knows these 3 MACs, that's okay.

If you are really doing routing or NAT, and doing it correctly, the ISP
knows one MAC (at most), your linux router's external interface. If
you're doing routing, then they know about all your IP addresses, but if
you're doing routing then they gave you those IPs in the first place.
It's more likely you're doing NAT, in which case they have no way of
knowing for certain how many machines you have.

--keith

--
kkeller-(E-Mail Removed)
(try just my userid to email me)
AOLSFAQ=http://www.therockgarden.ca/aolsfaq.txt
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Keith Keller <kkeller-(E-Mail Removed)> writes:

>On 2007-10-21, (E-Mail Removed) <(E-Mail Removed)> wrote:
>>
>> But ISPs know MACs, well that's what I heard, not sure if its true.

>Depending on their and your network architecture, they may or may not
>know your MACs.

MACs are only known on the subnet on which theirIP address is. Ie, it is
only for computers DIRECTLY connected to each other via ethernet.


>> say I have a linux router, there are 3 pcs behind it and having
>> internet acess. ISP knows these 3 MACs, that's okay.

No, the ISP does not know those 3 MACS. He only knows the MACS of your
router.



>If you are really doing routing or NAT, and doing it correctly, the ISP
>knows one MAC (at most), your linux router's external interface. If
>you're doing routing, then they know about all your IP addresses, but if
>you're doing routing then they gave you those IPs in the first place.
>It's more likely you're doing NAT, in which case they have no way of
>knowing for certain how many machines you have.


Agreed.

On 2007-10-21, Unruh <unruh-(E-Mail Removed)> wrote:
> Keith Keller <kkeller-(E-Mail Removed)> writes:
>
>>Depending on their and your network architecture, they may or may not
>>know your MACs.
>
> MACs are only known on the subnet on which theirIP address is. Ie, it is
> only for computers DIRECTLY connected to each other via ethernet.

That's right. So, hypothetically, one could imagine being on a cable
network over a hub, where your MACs would be available not only to the
ISP but to your entire network segment. (I think this scenario is
unlikely, but technically it's not impossible. The much more realistic
case is what's already been outlined.)

--keith

--
kkeller-(E-Mail Removed)
(try just my userid to email me)
AOLSFAQ=http://www.therockgarden.ca/aolsfaq.txt
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> but I wonder how are you using same public IP for all the computers?

I was just hypothesizing


> They cannot share the same (public) IP when they are in LAN, probably
> you might be using some private ip-range for them but proxying the
> internet network through the router. Could you Confirm?

That's true, I just wanna know if ISP can apply any kind of
restriction on this matter, based on the number of MACs being used

> Depending on their and your network architecture, they may or may not
> know your MACs.

So they can know it. Under what conditions?

> If you are really doing routing or NAT, and doing it correctly, the ISP
> knows one MAC (at most), your linux router's external interface. If
> you're doing routing, then they know about all your IP addresses, but if
> you're doing routing then they gave you those IPs in the first place.
> It's more likely you're doing NAT, in which case they have no way of
> knowing for certain how many machines you have.

Not me, I'm good with my ISPs, I was just wondering this situation.
But this pretty much answer the question.