In fact, this question is about openwrt and CoovaAP, but I guess it's the same in other linux distributions.
I've two interfaces, a "wan" and a "wlan" interface.
Is there by default any filter, which restricts which packets are forwarded from the wlan interface to the wan?
Especially if the wlan interface on the router is 192.168.1.1 and someone connected to this interface enters 172.16.1.1 as IP on his machine. Are his packets then forwarded anyway? Is the routing decision only made up by the destination IP or is it influenced by the source?
I think the problem would be that answers to the 172.16.1.1 machine wouldn't make their way back. Could the iptables forward rules make the interfaces behave like a switch?
If I wanted 172.16.x to be forwarded, I could setup an alias on this physical interface. Is there another way?
The default Coova firewall script just says
iptables -A FORWARD -i $WIFI -o $WAN -j ACCEPT
I disabled masquerading.
Is it possible to "separate" networks in this way and to rely on this? Is there a way someone could make his packets be forwarded with a not-192.168.1.x address?
The reason for this question is, that behind the WAN-interface are machines which should not be reachable for WLAN users. Those machines rely on the source-IP address.