Remote MySQL connection is not Working over ipv6, Have any Idea?

Question

define('QA_MYSQL_HOSTNAME', '251a:000:000:000:hv:c376:');

define('QA_MYSQL_USERNAME', 'user');

define('QA_MYSQL_PASSWORD', 'password');

define('QA_MYSQL_DATABASE', 'dbname')

Not working? 

Comments

But on define('QA_MYSQL_HOSTNAME', 'ipv4'); working fine