Re: MAC aliasing

[Kevin <kkadow_(_at_)_gmail_(_dot_)_com>]

>>> Mauro Calderara  wrote:
>>>> given that I have 5 NICs in the router, I thought that I could set
>>>> up a vlan-interface on those not directly connected to the 
>>>> cable-modem (they were supposed to inherit their's parent's MAC,
>>>>  right?) and bridge these vlans to the one NIC attached to
>>>>  the modem. 

I haven't tested this, but it does appear that by using the 'bridge'
interface to a second physical NIC on your server, you  can get the 
results you are looking for, without breaking any of the "rules" of 
Ethernet addressing (MAC uniqueness, etc).

I don't see any existing elegant solution to have OpenBSD originate,
accept, and process Ethernet frames showing a fabricated MAC.

My best guess is that this would require the creation of a new 'virtual'
NIC driver, similar to the existing 'bridge' driver but with the added
functionality of defining a hardware address for virtual interfaces, which
could then be joined to a bridge.


> > The thought has crossed my mind that creating a "virtual interface" on a
> > system you might be able to do such a thing.  OpenBSD does not have a
> > mechanism to create a "virtual interface" and define it's MAC.
> 
> Who has this feature, if any ?

VMware creates virtual interfaces with fabricated MACs when using
"bridged" interfaces in a virtual machine:
    http://www.vmware.com/support/esx/doc/set_mac_esx.html#macgen

A "VMNet" interface can be bridges, host-only, or NAT'd.  When a 
bridged interface is used, packets on the wire to/from the virtual machine
appear just as if it was a host on a real Ethernet bridge -- the packets show
only the new fabricated hardware address, not the host's true hardware
address.

Kevin Kadow