I’m facing 521 and 502 error on my website after I added CF dedicated SSL. Tried to whitelist CF IP on both GCP firewall and NGINX, but still no result. Then I use set the SSL type from “full” to “flexible”, then suddenly everything works fine. I removed CF IP that I whitelisted earlier on GCP firewall and NGINX, and the website still working fine. What does SSL ‘flexible’ mean? Does 'flexible" means less security?
Would appreciate any input.