I have the following:
A router with external ip address 209.xx.xx.xx. This router forwards to the ip address of the first rpi (rpi#1) (ports 80 and 443 to 192.168.1.170) and a random port (1234) to the second pi (rpi#2).
A domain name from noip.com forwards to rpi#1 via 209.xx.xx.xx. I added SSL (letsencrypt) to rpi#1. This is now secure (http -> https).
I have a second rpi (rpi#2) on 192.168.1.139 on the same router. The router forwards a port (1234) to rpi#2. This is not secure (http).
This is all working fine.
Now: I would like to add SSL to rpi#2. However, since noip.com can only forward to one external ip address, I can then not add SSL to rpi#2.
Any help greatly appreciated.