IPv6 and subdomain


I am starting to introduce IPv6 on my servers, it works fine. But when I am adding a subdomain, it does not work. The affected domain is reachable on IPv4 and IPv6 too.

Mxtoolbox can see the records, I can ping and ping6 on other servers, but not works in browser. My ISP supports only IPv4. If I change the alias to ip4.{domain} it works in my browser.

What could be the problem?

Thank you!

Hi dss

I could be wrong, but I’m thinking if your ISP only supports ipv4, then, those are the only domains it would resolve and pass to you in your ISP connection. Ie it cannot resolve ipv6 networks.

It is possible though, it IW may not have created AAAA record for subdomain, which if you can check and confirm. If it has not been created, please create it and test, but please be aware of the ISP ipv4 records only as above

There are ipv6 test sites on Internet, so you may want to google them and run an ipv6 test on both dns and website

I hope that helps

Many thanks


Dear John,
Thank you for your reply!
Yes, my ISP have only IPv4 support.
IW created A record for the IPv4, AAAA for the IPv6, CNAME for ftp, www and the other defaults.
It’s interesting, because the default CNAME records are working, only the subdomains not.
ipv6-test.com shows that the site is IPv6 ready.
It looks like subdomains (CNAME records) made at creating the account are working good only, the late added not.
Thank you!

Hi dss
Many thanks, and thinking about it quickly, I think the following (but could be wrong sorry)
IPV4 A domain.url 111.222.333.444
IPV6 AAAA domain.url fdf9:7db9:4817::
Cname domain.url
(Note the Cname only points to domain.url, and does not select which record IPV to use)
if connecting to website using IPV4 network, the resolution Cname should give you IPV4 A record
if connecting to website using IPV6 network, the resolution Cname should give you IPV6 AAAA record
If connecting to website using both IPV4 and IPV6 network, the resolution would only give you the IPV record which is higher preference, which I believe is IPV6, but could be wrong sorry and could be IPV4. This preference I believe would be at the users connection to broadband, not at the server connection.
I know Qmail would use IPV6 over IPV4 if both IPV were active on server, so if you have activated IPV6, please make sure you have RDNS setup correctly.
Many thanks

Hi John,
Your example is correct. I think, you’re right! Of course, my ISP can’t provide IPv6. :slight_smile:
Thank you!

It works perfectly! If the account uses IPv4 only I had to wait ca. 5-10 mins, if uses IPv6 too it was ca. 45-60 mins.