I am trying to make a comparison test between two different NetBSD Packet Filter pf implementations and I want to use the following testbed :only two machines with 2 inerface cards each:sender-receiver machine and gateway.
1-->sender interface(eth0 and receiver interface(eth1;for this machine forwarding is disabled;
2-->gateway with wm0- and wm1-;for this machine forwarding is enabled;
The problem is I don't manage to obtain a correct configuration:when I try to ping from sender interface to receiver interface through the gateway
I can see with wireshark the requests on the receiver interface,but this interface is not replying in turn.
ping -I eth0 or ping -I eth1 has the behavior explained above.

Any information would be very useful.Thank you!