Services

I have a IP phone and the problem is that it dont work behind a firewall.
It is possible to use DMZ to forward white IP from my ISP and not use 192.168.1.XXX?

On another interface, yes. Or you could use 1:1 NAT with an additional public IP, but if NAT breaks your phone regardless that won't help. You can't mix subnets on the same broadcast domain/physical network, so only 192.168.1.x (or whatever your LAN subnet is) IP's can be used on your LAN.