MySQL server:
IP: 192.168.0.1
user: testing
pass: testing123123

MySQL client #1:
IP: 192.168.0.2

MySQL client #2:
IP: 192.168.0.3

GRANT ALL PRIVILEGES ON *.* TO testing@'192.168.0.2' IDENTIFIED BY 'testing123123';
flush privileges;

mysql -h192.168.0.1 -uuser_bla_bla -pbla_bla_bla
ERROR 1045 (28000): Access denied for user 'user_bla_bla'@'192.168.0.2' (using password: YES)

2017-03-11 12:13:10 82588 [Warning] Access denied for user 'user_bla_bla'@'192.168.0.2' (using password: YES)

mysql -h192.168.0.1 -uuser_bla_bla -pbla_bla_bla
ERROR 1130 (HY000): Host '192.168.0.3' is not allowed to connect to this MySQL server

[mysqld]
log_warnings = 2
log_error=/var/log/mysql_error.log