On Friday, 01/23/2009 at 05:53 EST, Mark Post <[email protected]> wrote:

> s390a13:~ # ifconfig
> bond0     Link encap:Ethernet  HWaddr 02:00:00:00:00:06
> eth1      Link encap:Ethernet  HWaddr 02:00:00:00:00:06
> eth2      Link encap:Ethernet  HWaddr 02:00:00:00:00:06

> Adapter 0800  Type: QDIO      Name: UNASSIGNED  Devices: 3
> Port 0 MAC: 02-00-00-00-00-06  VSWITCH: SYSTEM VSW1
>      RX Packets: 27573      Discarded: 281        Errors: 0
>    Unicast MAC Addresses:
>       02-00-00-00-00-06

> Adapter 0900  Type: QDIO      Name: UNASSIGNED  Devices: 3
> Port 0 MAC: 02-00-00-00-00-0C  VSWITCH: SYSTEM VSW1
>      RX Packets: 20         Discarded: 7          Errors: 0
>    Unicast MAC Addresses:
>       02-00-00-00-00-06 IP: 10.10.220.13

Good.  That confirms my assertion that CP will not allow two NICs to have
the same MAC.  Since the guest constructs the MAC headers on a layer 2
VSWITCH, it can put whatever it wants.  I.e. a frame can leave 02::0C and
have "from" as 02::06.  But since the actual MAC isn't changed, all
unicast inbound traffic will enter only a single NIC (even if both answer
the ARP).

But I would have expected an (obvious) error when Linux tried to change
the MAC address on 900.  There is something about this that I'm not
understanding.

Alan Altmark
z/VM Development
IBM Endicott

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