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Forum Discussion
NAT Hairpinning/Loopback Not Working
I have noticed that NAT hair pinning only seems to work with *manual* port mapping, not UPnP / NAT-PMP.
Your guesses are correct.
Any UPnP (or NAT-PMP) application would suffice to reproduce the issue. I used Port Map for macOS https://www.codingmonkeys.de/portmap/ but really any would have the same effect, since the option to hairpin is not part of the UPnP or NAT-PMP protocols.
Thanks for the quick response. "Over my head" (oh, dear). Being a Philistine (Windows user), it is not clear to me how to activate UPnP and demonstrate that it is actually working. My example (see messages above) about the Epson printer was based on the printer already having an http web server.
Do I need to set up a web server on my Windows PC that can use UPnP to open a port? Or.......????
I'd really like to validate that ports forwarded because UPnP opened them behave differently than ports opened deliberately, but have no clue how to do it.
If ignorance is bliss, then I must be in heaven.