Problem with unkownHost after several hours

Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g., so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.

My domain is:

I ran this command:

sudo certbot --authenticator webroot --webroot-path /var/www --installer apache

It produced this output:

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator webroot, Installer apache

Which names would you like to activate HTTPS for?


Select the appropriate numbers separated by commas and/or spaces, or leave input
blank to select all options shown (Enter ‘c’ to cancel): 1
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for
Using the webroot path /var/www for all unmatched domains.
Waiting for verification…
Cleaning up challenges
Failed authorization procedure. (http-01): urn:acme:error:unknownHost :: The server could not resolve a domain name :: No valid IP addresses found for


  • The following errors were reported by the server:

    Type: unknownHost
    Detail: No valid IP addresses found for

    To fix these errors, please make sure that your domain name was
    entered correctly and the DNS A/AAAA record(s) for that domain
    contain(s) the right IP address.

My web server is (include version):

Server version: Apache/2.4.18 (Ubuntu)

The operating system my web server runs on is (include version):

Ubuntu 16.04

My hosting provider, if applicable, is:

I can login to a root shell on my machine (yes or no, or I don’t know):


I’m using a control panel to manage my site (no, or provide the name and version of the control panel):


I have tried to create a certificate with the help of letsencrypts and certbot. It has worked previously on other servers that I own but did not for this one. I got the message I pasted above which suggests that letsencrypt cannot find my server, however when I use my browser and when I use dig (dig or dig @ it gives me the right IP-address. I am not an expert with these things so I would really like some help figuring out why this isn’t working…  (signed)  3515  A

That isn’t a public IP address. It’s a private, shared IP address reserved for Carrier-Grade NAT, similar to how 192.168.x.y addresses are for local networks.

You need a public IP address, IPv4 or IPv6, for Let’s Encrypt HTTP validation.

You can use DNS validation instead, but if you want to run a public website, you would still have a problem…

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