Redirecting ports in a bridge

Hi.
I have a linux appliance from Eneo Tech. (http://
www.eneotecnologia.com/) with the following setup:

(192.168.1.x)
192.168.1.7 ----
SERVER1 192.168.2.1
[ LAN1 ] ----------- [ ROUTER ] ---------- [ APPLIANCE ] --------
[ LAN 2 ] --------|
192.168.2.7 192.168.2.140
(192.168.2.x) ---- SERVER2 192.168.2.2

The appliance has 4 ethernet cards, and a br0 bridge which includes
all them. ETH2 is connected to the router, ETH3 is connected to LAN2,
and BR0 has an IP address of LAN2.

Now, I want to redirect all HTTP traffic going to SERVER1, to the same
port SERVER2.

I've tried the following rule:

iptables -t nat -A PREROUTING -p tcp -d 192.168.2.1 --dport 80 --to-
destination 192.168.2.2:80 -j DNAT


The redirection seems to be working, as far as I've seen with tcpdump
on SERVER2, but I'm not able to make a connection.

I have two suppositions:

1) I have to SNAT the response. I've tried that rule:
iptables -t nat -A POSTROUTING -p tcp --sport 80 -s 192.168.2.2 -d
192.168.1.0/24 -j SNAT --to-source 192.168.2.1

2) I have to use ebtables, as I'm using a bridge.

Any help? Thanks in advance :-)