IP or pool ip for get ssl?

My ISP is blocking everything in my path.. Which IP or IP pool do I need access to and on what ports to receive ssl?

validate my web server?
Let’s Encrypt does not publish a list of IP addresses we use to validate,
and these IP addresses may change at any time.

Let's Encrypt uses Multi-Perspective Validation Improves Domain Validation Security - Let's Encrypt

Please read these as well.