Messages in this thread |  | | Date | Mon, 19 Aug 2002 14:00:18 -0500 (EST) | From | "Mark H. Wood" <> | Subject | Re: ethtool documentation |
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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".
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