Actually, the main domain example.com redirect to a VPS with an IP like IP-A. On another hand, I have a Synology server, joinable at synology.example.com, with another different IP : IP-B.
The problem is if I try to get SSL certificate from the Synology, it doesn’t work, obviously because the challenge is sent to example.com, wich reach IP-A, whereas the let’s encrypt request has been sent from IP-B.
What is the simpliest way to proceed with Synology? Generating the certificate from the VPS on IP-A and then export it to the synology? Will I have to repeat this each time the certificate will be renewed? Or another process maybe?
This shouldn't be the case. When you properly request a certificate for synology hostname, the challenge should verify that hostname, not your main domain name.
Well, my bad… I’m pretty sure there was a time where Synology didn’t accept something else than example.com in the “domain” input field. So I didn’t even try…
Everything works fine, thanks for your answer it did the trick even if it was obvious…