I wonder if you could accomplish what you want using
iptables. Looking through the
iptables man page I noticed this option called
The TEE target will clone a packet and redirect this clone to another
machine on the local network segment. In other words, the nexthop
must be the target, or you will have to configure the nexthop to forward
it further if so desired.
Send the cloned packet to the host reachable at the given IP
address. Use of 0.0.0.0 (for IPv4 packets) or :: (IPv6) is
To forward all incoming traffic on eth0 to an Network Layer logging box:
-t mangle -A PREROUTING -i eth0 -j TEE --gateway 2001:db8::1
It would seem that a command like this would do what you want:
$ iptables -t mangle -A PREROUTING -i eth0 -j TEE --gateway <ip address>
Also there is this tutorial titled: Howto: Copy/Tee/Clone network traffic using iptables, that covers how to use it in a little further details.