> > All I'm saying is that there is nothing wrong, > > standards-wise, in having *one* globally unique MAC address per box. > > But I'm disagreeing. > > There is a lot wrong with having the same address on multiple ports of a box, > when those multiple ports share the same network. This is true both at layer > 2 and at layer 3, right?
For more info see for instance the following comp.dcom.lans.ethernet message from Rich Seifert: https://groups.google.com/group/comp.dcom.lans.ethernet/msg/dbe062f75538718d?hl=en&dmode=source&output=gplain <quote> Which is exactly why I said MAC addresses are not *ordinarily* assigned to CPU ports. Sun uses (used?) the model that I actually prefer, i.e., that the MAC address identifies the *station*, rather than the network interface. There is a discussion of these two models in "The Switch Book," excerpted here: "There are actually two philosophies for interpreting unicast addresses. One philosophy follows the premise that a unicast address identifies a device (e.g., a workstation or server), as opposed to a network interface installed within the device. Under this philosophy, when a device has multiple interfaces, it uses the same address on all of them. This approach was used in the original Xerox Network System (XNS) and most Sun Microsystems' products. The other philosophy, that an address uniquely identifies the interface rather than the device, sees more widespread application today, and is the model assumed in this book (even though the author has an affection and longing for the 'architectural purity' of the single address per device model). Using the address-per-interface philosophy, a device with multiple interfaces will have multiple unicast addresses assigned to it. Both philosophies are valid, in the sense that both can be made to work properly in a practical network. In neither case is there any ambiguity about the destination for a frame sent to a given unicast address." </quote> However, this is getting rather far away from the *practical* problem of DAD in the face of several boxes with the same MAC address on the same LAN segment. Steinar Haug, Nethelp consulting, sth...@nethelp.no -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
