Looked at them now (till before just found only the official instruction). Unfortunatly, I cannot apply neither of them: my ISP is using a custom version of firmware that block me out (I'm just a super user, but not a full admin of the modem) from many configurations, including telnet access and configuration files. The model is set to redirect (DMZ) all the traffic to a better router. Now I tried to explicity forward such ports from the router. Let's see how it work....