Yes
EDIT: AFAIK, there are three things that can affect how the port forwarding will work....
- The SDK (and therfore the netfilter modules) for the router. In this case, each router that uses a different SDK MAY behave differently....an N66 may be different from an AC68 which may be different from an AC3200....
- The miniupnpd implementation. This should be the same across all of Merlin (and my fork), but may be different for ASUS firmware vs DD-WRT vs Tomato...
- The creation and ordering of the firewall rules, which again will be different depending on the firmware stream being used. In this case, even my fork is different from the latest Merlin.
EDIT2: Something to think about with respect to Full Cone NAT. According to some of the references previously posted, my take away is that it's defining characteristic is that it will accept UNSOLICITED packets, just like defining a manual port forward. Do you really want an application to have the ability to open a random port fully to the internet? In my mind, that's why game manufacturers need to move away from that as a requirement, and why most routers have already restricted that capability.