Mailinglist Archive: opensuse (3863 mails)

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Re: [SLE] Comcast and NAT
  • From: "Carlos E. R." <robin1.listas@xxxxxxxxxx>
  • Date: Wed, 4 Feb 2004 21:49:54 +0100 (CET)
  • Message-id: <Pine.LNX.4.53.0402042128400.8319@xxxxxxxxxxxxxxxx>

The Tuesday 2004-02-03 at 22:49 -0500, Paul W. Abrahams wrote:

> > MAC addresses were supposed to be world wide unique: a part of the
> > address identified the card maker, the rest the card itself; of course,
> > that doesn't mean you can find any computer given the mac address. And MAC
> > addresses can be spoofed, so all this might not be true nowdays.
>
> The confusion arises because what is true in particular is not true in
> general. For Comcast customers (and presumably those of some other net
> vendors also) it is true that you can find the hostname of the customer's
> computer if you know its MAC address. But it is emphatically not true that
> you can find the hostname (or IP address) of an arbitrary computer, given its
> MAC address.
>

I understood that already :-)

But that was not my meaning. MAC hardware addresses, or ethernet
addresses, in numeric form, were designed originally to be universally
unique, in hardware, unchangeable. Card makers applied for a registered
maker number, and then added serial numbers of their own, never repeating
a number. Thus, any card on the world was supposed to have unique
numerical hardware addresses. I stress "supposedly" :-)

Nevertheless, that doesn't mean you can reach any computer by it's MAC
address, unless it is on your ethernet LAN.

On the other hand, there is that interesting trick of Comcast of using an
internet naming scheme with names formed from the mac address. Interesting
trick, it's new for me.

I hope I clarified my meaning? :-)

--
Cheers,
Carlos Robinson


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