Help understanding SSL certificates

Hi all,

I am new to using SSL certificates and trying to understand if I am setting my system up securely. Right now I have Hassio running on a RPI3B+. I set up DuckDNS to handle accessing from outside my network and that has worked well. I have the the fullchain and privkey files saved to the SSL folder so they can be used by other add-ons, again, that works how it should.

Where my confusion comes in is with how I connect an external pi that is actin as my database server and running InfluxDB/Node Red and a third Rpi running PiHole and acting as my DHCP/DNS server. Having a limited understanding of SSL certs, how do I set up my other two Pis to be able to talk to my HA server via SSL authentication? Do I use the same pem files I use for HA? Where do they go on the other devices as well?

If the external servers are on your local network, they should not need to be secured with ssl to protect you. All the Internet Hassio traffic flows through https using your ssl certificate.