Re: ethtool documentation

[Mark H. Wood]

On 6 Aug 2002, Alan Cox wrote:
> On Tue, 2002-08-06 at 21:42, Randy.Dunlap wrote:
> > Do you mean several unicast MAC addresses, as opposed to
> > broadcast + several multicast + (one) unicast MAC address?
> > If so, I'm not familiar with that scenario.
>
> Two unicast addresses, one for the sane world one for DECnet. The DEC
> tulip supports this as one example

Yes indeedy.  This is what DECnet Phase IV has instead of ARP.  Rather
than broadcast a query and hope someone answers with the desired mapping,
Phase IV specifies a mapping formula so that the sender can simply
calculate a MAC address for any neighbor, given its upper-level address.
That's where those AA-00-04 addresses come from -- the lowest 16 bits are
the DECnet area and node number.  There are a number of well-known
multicast addresses (AB-00-04) too.

Notice something that nobody has brought up yet (unless it's in the 3000
messages I haven't caught up to yet, sorry):  LAA and UAA addresses can
always be distinguished, by a bit in the top end.  You can manufacture all
the LAAs you want and namespace collisions are your problem, but UAAs are
expected to be unique and unchanging.

-- 
Mark H. Wood, Lead System Programmer   [e-mail]
MS Windows *is* user-friendly, but only for certain values of "user".