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I'm using [Traefik]( in my server which has built-in feature of generating Let's Encrypt certificates for my domains.

However, when I deploy my traefik stack, I get this error:

Unable to obtain ACME certificate for domains \",\": 
unable to generate a certificate for the domains []: 
error: one or more domains had a problem:\n[] acme: error: 400 
:: urn:ietf:params:acme:error:connection 
:: Timeout during read (your server may be slow or overloaded), url: \n" 
rule="Host(``) || Host(``)"

Some observations: 

- I have other domains in my stack and traefik was able to generate certificates for those. (e.g. it was able to create certificates for,

- I can ping my ipv4 address,, and also the ipv6 address using this [tool](

- It was suggested in the [Traefik forum]( to check...

	> that you can curl on both IPv4 and IPv6 the ip mentioned in the A and AAAA records for the faulty 	domains?

	When I run `curl my.ipv4.addr.ess` -- I get a `404 page not found` and when I `curl  my:ip::v:6:add:ress` I get `curl: (3) IPv6 numerical address used in URL without brackets`


What could be causing this issue with generating certificates?
Top Answer
Once I removed the AAAA records of and, traefik was able to generate certificates for them.

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