Network case:
Source--Routers ... eth0=LINUX=eth1 ---- some routers.. -- Destination
2.2.2.2 10.0.0.1 192.168.0.1 1.1.1.1
and 1.1.1.0/24 via 192.168.0.100 dev eth1
Packet coming to eth0 interface with src:2.2.2.2 and dst:1.1.1.1, need to be forwarded onto eth1 interface.
After some tests, I found that with "net.ipv4.ip_forward=1", LINUX can forwards only to local reachable destination (that can be reachable via same broadcast domains, eg:192.168.0.2), but not remote destinations.
This is not the case of NAT and packets are not destined to IP on local interfaces.
This is the case of a regular Router behavior, doing routing (not only forwarding).
I suppose that is can be done somehow with iptables rules.
Any suggestion would help. Thanks