Re: [ProgSoc] Made in Taiwan

[Matt <matt@nospam.telesales.zip.com.au>]

On Wed, May 19, 1999 at 09:52:49PM +1000, Matt Beauregard wrote:

> On Wed, May 19, 1999 at 09:39:06PM +1000, gleNN wrote:

>> Sounds pretty reasonable, but why is the Ethernet address in EEPROM
>> to start with? It shouldnt be able to be fiddled with or trampled
>> upon.

> The ability to modify a card's MAC address is actually mandated in
> some standard or other, IIRC.

DECnet requires you to be able to set the MAC address (the last 6 hex
digits). this is because those are set by your local network server
(forgotten the name of them). this works somewhat similar to the
AppleTalk method of allocating station addresses.

the first 6 hex digits will tell you who manufactured the card and
this should not need to be set.

btw i have heard alan cox mention that some drivers and cards have
problems because the EEPROM sometimes dont have the address
initialized on them properly *shrug* search l-k and check for alan and
eternet stuff.

As far as A5:A5:A5:A5:A5:A5 goes, this is a fault address. If you ever
put a good ethernet debugger on a line, you will find half sent
packages (remember that ethernet is CDMA (collision detect multiple
access not code division multiple access)) are given the A5A5A5A5A5A5
address (as the ethernet source address). i think the ethernet frame
preamble might be a A5A5A5 sequence as well, but you'd need to check
the 802.2 and 802.3 spec documents.

what does this mean for you? well if your memory was overrun (by
something going awry) it is unlikely that it would have happened in
such a uniform manner. it would seem more likely to me that this is an
indicator that something is wrong with the card and this might be a
well defined failure mode (where it is defined is another matter :P).

	matt

p.s. the above is mostly from memory, past experience and some
speculation.
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