I was reading an article on how TOR has NAT piercing properties and I need to ask please:

What is NAT piercing (in relation to the TOR network) and how does NAT piercing help the TOR network.

And also, is NAT piercing the same as NAT punching? I see NAT punching come up in search results when I search for NAT piercing

1 Answer 1


"NAT piercing" aka "UPNP punching" is the way to open a port on a NAT router to be forwarded back to you. It needs an "upnp-helper" that can be configured inside the torrc config. The original upnp-helper is still available in a source code, but iy's a way too obsolete. My advice to you - make a static IP+port mapping, it works just fine, but if you're explicitly needing the piercing functionality - make your own helper, running as an independent service

  • Thank you for your response. In a bid to convey my question right. Let's consider the statement 'TOR has NAT-piercing properties'. Does this mean that a computer hosting a .onion address behind a NAT is accessible to the outside world/network without having to set up port forwarding on the router? I know that in the case of setting up an ordinary web server on a computer behind a NAT, you would need to set up port forwarding. Does this case apply to Tor? Still trying to personally set up a tor server behind a NAT so this would be clearer for me.
    – Joker
    Nov 19, 2021 at 17:08
  • Yes, if NAT will be "pierced" or "UPNP-punched" - it will be a temporary port forwarding set up. The end result is always the same : a LAN IP address with an open port is visible from outside via port forwarding. If you're doing as I suggested - the static address and the static port forwarding rule - you're doing it once and it works. If you're piercing nat - you're doing exactly the same thing each time you're starting Tor
    – Alexey Vesnin
    Nov 20, 2021 at 20:19
  • Okay. Thank you so much, will check out and revert
    – Joker
    Dec 3, 2021 at 12:50

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