network load balancing & multicast mac-address

Hi,
As a part of a network load balancing/HA solution configuration, our
solution provider partner asked us to configure the same multicast
mac-address on 2 Cisco Catalyst 3550 ports and on 2 Debian Gnu/Linux
server, assigning this multicast mac-address to the dummy0 interface of
the server, configured with the same IP address.
The software (perl+iptables) implemented by the provider should be
able, somehow, to 'tag' incoming packets' (like even/odd) and thus to
make a redirection to one server or to the other one.
After a couple of tries sniffing packets, we were able to see packet
reaching the switch ports and the physical interfaces, but no packet
came back from the dummy0 interface; it was possible to 'ping' the
dummy0 interface and to get an ICMP reply, but only while running a
tcpdump on the phisical interface; we were unable to get any tcp reply
from the dummy interface, like executing a 'telnet 192.168.20.101 80'.

A couple of questions:
Is such a solution possible at all, or is a confusing one?

Is the /etc/network/interfaces configuration correct?:

---------------------
auto dummy0
iface dummy0 inet static
address 192.168.20.101
netmask 255.255.255.255
hwaddress ether 09:09:09:09:09:09
up /sbin/ifconfig dummy0 promisc up
---------------------

Thanks a lot in advance
Any help is really appeciated

.