Yes. Your resellers simply need to configure their domain names with an A record pointing to the IP address of your Centova Cast web interface (or a CNAME record pointing to the existing domain name of your Centova Cast web interface). This change is made on your reseller's end, either in your reseller's web hosting control panel, at your reseller's domain registrar, or in your reseller's nameserver configuration files.
No configuration changes are required in Centova Cast; once the DNS changes are made and the changes have time to propagate, the reseller and his clients should be able to access Centova Cast at http://reseller-domain.xyz:2199.
