I need to ask a question about network port forwarding, but I don't know where to ask it.
Somewhere else completely?
Yes, those two sites (and Server Fault) come to mind. It's largely a matter of whether you're asking a 'professional' or 'consumer' question:
Network Engineering Stack Exchange is for asking questions about professionally managed networks in a business environment.
(Note: All questions about RESIDENTIAL/HOME networking and CONSUMER-grade equipment, are explicitly OFF-topic.)
(from the Network Engineering Help Center)
Server Fault is for questions about managing information technology systems in a business environment.
If your question is about:
- managing the hardware or software of servers, workstations, storage or networks
and is not about:
- consumer workstations or networking (which belong on our sister site, Super User)
(from the Server Fault Help Center)