arp question

[Stephane Couture <muscou@sympatico.ca>]

Not sure if this is the right forum but any help would be appreciated. 

My NIC support up to 16 unicast MAC address which can be assigned to 
different H/W queue.  The cpu is only connected to one ethernet network 
and all packet destined to a specific subnet are routed over PCI (not as 
is, multiple packets manipulations are done beforehand).  I am trying to 
make use of this feature to, hopefully, enable faster routing.

 I would like to assign a different MAC for a specific subnet and 
respond to arp request for that subnet.
- Current proxy-arp implementation is not what I want.  Proxy-arp with 
subneting seem to be what I need but it does not seem to be supported 
anymore (as of 2.2?). 
- Adding arp entry with the publish flags disregard the provided address 
and use the one from the network interface.
- constant gratuitous ARP on the entire subnet could work but I am not 
sure about the reliability of this method.

I'll modify the kernel (2.6.20) if I have to but there has to be a 
simpler way. 

Thanks.