I configured my DNS (bind9) to accept every subdomain, using a wildcarded 'A' record :

*.mydomain.tld.      IN    A         xx.xx.xx.xx

I configured Apache to serve some specific subdomains using virtual hosts :

<VirtualHost *:80>
        ServerName sub1.mydomain.tld
        ServerAlias sub1.mydomain.tld
        JkMount / sub1JK
        JkMount /* sub1JK
</VirtualHost>

when I ping from a remote computer on a subdomain configured in apache I get a response. When I ping on a subdomain that is not configured in apache, the host is not found.

I don't understand why apache configuration would affect DNS resolution like this?

I would appreciate any information that helps me understand this.

Thanks a lot.