Incoming ports on gateway router

Simple n00b question. I have searched the forum but found no specific answer.

If I have a gateway on a network do I have to open any incoming ports on the router to allow a connection from outside the local network?

For example, I am currently running a gateway at home. It is connected to my home network and working well. However, I wonder if I need to configure my home router to allow something from outside to establish a link with the gateway. Later I will move the gateway and connect it to a cellular modem. The same question applies.

I’m looking for a clear yes/no answer, but I’d be happy with “it depends” with a list of reasons why I might want to open a port, and the consequences if I don’t open any.

Thank you.

The aging but traditional protocol uses UDP, in a fairly ordinary and expected way. Although UDP is connectionless, firewalls and NAT solutions realize that replies are typical, and so effectively dynamically open allowance for the reverse path upon seeing the outgoing one.

Normally this should work fine, though there have been claims of oddities when two gateways are on the same subnet.

Ok. Thanks for your reply. So basically all communications are initiated by the gateway going “out”? There are no communications initiated by the server?

Correct. There is no need to forward any incoming port.

Great! Thanks! That makes things easy.

Of course I may want to open a port for maintenance of the gateway from “outside”, such as ssh (port 22) but that’s a different matter. My main concern was knowing if a port is required for TTN itself, and it’s not.


Consider a reverse tunnel to a bastion host. Or some people are using VPNs.