Very Computer

Hi everybody,

I'm looking for a way to get some unique system identification (globally
unique I mean)

I need a key that is unique for each system in a network ...

Thanx

Wim Delvaux

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:>
:> > I'm looking for a way to get some unique system identification (globally
:> > unique I mean)
:> >
:> > I need a key that is unique for each system in a network ...
:> >
:>
:> If they have Ethernet cards, the Ethernet addresses are unique
:> in the known universe.

: usually... and they can also usually be changed via software.  pc's don't
: have any kind of cpu-encoded serial number, though, so ethernet address
: isn't much good for commercial type stuff.  if it's just as a simple
: identifier, though, yes it will work - in fact, if it's not unique, it can
: cause some interesting problems... ;*)

I can see changing the software (IP) address.  But I know of no way to
change the "hardware" address.  In fact, this is vendor specific as well
and is supposed to be "hard" (unchangable) so far as I know...  note
that we are talking about the so-called "hardware ethernet address"
here...

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: :> If they have Ethernet cards, the Ethernet addresses are unique
: :> in the known universe.
:
: : usually... and they can also usually be changed via software.  pc's don't
: : have any kind of cpu-encoded serial number, though, so ethernet address
: : isn't much good for commercial type stuff.  if it's just as a simple
: : identifier, though, yes it will work - in fact, if it's not unique, it can
: : cause some interesting problems... ;*)
:
: I can see changing the software (IP) address.  But I know of no way to
: change the "hardware" address.  In fact, this is vendor specific as well
: and is supposed to be "hard" (unchangable) so far as I know...  note
: that we are talking about the so-called "hardware ethernet address"
: here...

Nope, even that is changeable.  We had in our company a faulty Ethernet card,
so the vendor (HP in this case) came and replace it.  The guy that replaced
it asked whether we wanted the same hardware Ethernet address as the old card
and when we answered 'yes', he changed it.

From what I've heard you can only do it once, so the guy didn't really 'change'
it, but 'set' it.  But I suppose it is somewhere in a flash prom that you
could reset...

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: Nope, even that is changeable.  We had in our company a faulty Ethernet card,
: so the vendor (HP in this case) came and replace it.  The guy that replaced
: it asked whether we wanted the same hardware Ethernet address as the old card
: and when we answered 'yes', he changed it.

: From what I've heard you can only do it once, so the guy didn't really 'change'
: it, but 'set' it.  But I suppose it is somewhere in a flash prom that you
: could reset...

I wonder what he set.. IE the high-order part is mandated to vendor-specific
codes.  Maybe the lower-order end is done with PLA's or something...

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(205) 934-5473 FAX              Birmingham, AL 35294-1170

Thanx for the response.

Unfortunately, the IP address thingy is not OK.  The systems might not be
connected to the
network ( all the time ).

The MAC address thing is better but not all systems do have a LAN
connection (eg ppp)

Someone has suggested that one could also detect the volume identification
of the hard disk

- How do I program this
- Does the mechanism depend on the type of dist (e.g. SCSI, IDE, ...)

Thanx

  rh> I can see changing the software (IP) address.  But I know of no
  rh> way to change the "hardware" address.  In fact, this is vendor
  rh> specific as well and is supposed to be "hard" (unchangable) so
  rh> far as I know...  note that we are talking about the so-called
  rh> "hardware ethernet address" here...

Some Ethernet cards really do allow you to change the MAC address.

        Stefan

Bye, Juergen

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HOwever, the Ethernet specs require that there is a way to change the
effective MAC address during actual operation (a non-permanent change
that is achieved via software, and disappears when you reset the
card). This is so that old protocols, which use MAC as a routing code,
can work. An example of such protocol is DECnet, where a network node
ZONE.NODE (e.g. 1.234) is reprogrammed to have MAC address of
AA-00-04-00-xx-yy, where NODE = ((yy*256+xx) mod 1024) and
ZONE=(((yy*256)+xx) % 1024)

DEC original MAC addresses have a form of 08-00-2B-....

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| HOwever, the Ethernet specs require that there is a way to change the
| effective MAC address during actual operation (a non-permanent change
| that is achieved via software, and disappears when you reset the
| card).

See "man ifconfig," depending on your version the option is called
either "mac" or "hw" and does just this.
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In newsgroup: comp.os.linux.development.system

Quote:

> I wonder what he set.. IE the high-order part is mandated to vendor-specific
> codes.  Maybe the lower-order end is done with PLA's or something...

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