Nginx IPv6 configured according to docs, but IPv6 test sites report failure

I've got an Nginx server block that looks like this:

---

Code:

server    {
      listen             80;
    listen            [::]:80;
    #listen             443 ssl;

      server_name         mydomain.com;
     ...location directives, etc...

According to previous posts here and elsewhere, that should tell Nginx to listen on IPV6. Nginx starts just fine.

When I check the site using an IPV6 validator like IPv6 test - web site reachability it says my DNS settings are correct, but fails because the web server isn't accepting connections.

I looked through various Nginx conf files, and everything looks normal. Unfortunately my home Comcast cable service is still IPV4 only, so I can't manually curl the server via ipv6.

Nginx error logs look fine to me, not seeing anything amiss.

What could possibly be causing this?
It's a plain vanilla Centminmod install, beta .08 for Centos 7 that I installed last night on a new Ramnode VPS.

 

Actually, the site you linked to only checks the DNS readiness, it doesn't ping the webserver itself. That website reports my site as working correctly for IPV6, even though it's not.

As I mentioned in my post, DNS isn't the issue--the packets are getting routed to the correct server. It's just something is misconfigured within my server.

I'm not sure if CSF firewall is intercepting the packets before Nginx sees them, or which Nginx log to check (there's both a general error log and a per-domain error log).

Any suggestions on things I can use to debug where the root cause is are appreciated.

 

Also, might want to add a "[::]:80 default_server;" line right after the similar line for IPv4 in this file: centminmod/virtual.conf at 123.08centos7beta02 · centminmod/centminmod · GitHub

That way nobody gets bit by having the wrong site served on a domain if they forget to specify the default_server directive: nginx: how to specify a default server | The Gahooa Perspective

Adding that line may cause startup issues if Nginx isn't compiled with IPv6 support, I don't know.