Do you mean that you have 2 devices and you want to forward the same inbound port to both devices? For example, you want to forward port 1234 to 192.168.1.1 but you also want to forward it to 192.168.1.2 at the same time? That's not possible on any device because it doesn't make sense. What if both devices are on at the same time? Which one is supposed to respond?
There are workarounds you can do by forwarding different inbound ports to the same destination port but you would need to provide more details such as the particular port/service you want to forward if you want help with those.
