Do you have any idea which IP addresses Let’s Encrypt uses for the HTTP-01 challenge?

Help
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Do you have any idea which IP addresses Let’s Encrypt uses for the HTTP-01 challenge?

So basically, I want to whitelist those ip address on my firewall.

Thanks,
Pardeep

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They use many, from around the world, that keep changing. This is so that they can verify that the entity that is trying to get a certificate for a domain name actually controls the domain worldwide.