: Cannot access the subdomain all the time I created a new subdomain: blog.example.com. Sometimes, the blog is accessible without any problems, but other times it's not, just like now at this moment

@Eichhorn148

You have a problem with the nameserver (NS) records for beiruthub.com.

$ dig NS beiruthub.com

;; ANSWER SECTION:
beiruthub.com. 1800 IN NS dns1.m6.net.
beiruthub.com. 1800 IN NS dns2.m6.net.
beiruthub.com. 1800 IN NS dns3.m6.net.
beiruthub.com. 1800 IN NS ns01.domaincontrol.com.
beiruthub.com. 1800 IN NS ns02.domaincontrol.com.


You are specifying two companies as handling your DNS: m6.net and domaincontrol.com. This is usually a mistake. You usually want to have one company handling your DNS. Otherwise you have to keep your DNS records in sync between two different companies.

Indeed, in your case, the m6.net server knows about blog but the domaincontrol.com server doesn't know about it.

$ dig @dns1 .m6.net blog.beiruthub.com
;; ANSWER SECTION:
blog.beiruthub.com. 86400 IN A 67.228.172.101

$ dig @ns01 .domaincontrol.com blog.beiruthub.com
;; Query time: 165 msec
;; SERVER: 216.69.185.1#53(216.69.185.1)
;; WHEN: Thu Nov 14 07:06:06 2013
;; MSG SIZE rcvd: 115


The reason that it works only some of the time is that the DNS entry is sometimes fetched from the m6.net servers (and it works), and is sometimes fetched from the domaincontrol.com servers (and it doesn't work).

You will probably want to remove the domaincontrol.com records from your DNS NS records. They can be edited through your domain registrar.

Removing the extra NS records may take a day or more to resolve the problem. In the meantime you could also add the A record for blog.beiruthub.com to the domaincontrol.com servers so that it can be resolved no matter which name server is chosen.

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