IT WORKS!
Finally!
The newly created modem interface must have a random IP in the modem's subnet and not the IP of the modem itself. That was what I was doing wrong!
Thank's a lot @moeller0 !
So... to sum up:
-
If the LEDE router is at 192.168.1.1 , set the modem at a different subnet, e.g 192.168.2.1
-
Create the modem interface in /etc/config/network
config interface 'modem'
option ifname 'eth1'
option proto 'static'
option ipaddr '192.168.2.100'
option netmask '255.255.255.0'
- Add modem at the wan zone in /etc/config/firewall
option network 'wan wan6 modem'
And you're done!
Once again thank's a lot guys!