Re: ethtool documentation

From: Mark H. Wood (mwood@IUPUI.Edu)
Date: Mon Aug 19 2002 - 14:00:18 EST

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   mwood@IUPUI.Edu
MS Windows *is* user-friendly, but only for certain values of "user".

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to More majordomo info at Please read the FAQ at

This archive was generated by hypermail 2b29 : Fri Aug 23 2002 - 22:00:17 EST