This grants root access with the same password from any machine in *.example.com
:
GRANT ALL PRIVILEGES ON *.* TO 'root'@'%.example.com'
IDENTIFIED BY 'some_characters'
WITH GRANT OPTION;
FLUSH PRIVILEGES;
If name resolution is not going to work, you may also grant access by IP or subnet:
GRANT ALL PRIVILEGES ON *.* TO 'root'@'192.168.1.%'
IDENTIFIED BY 'some_characters'
WITH GRANT OPTION;
FLUSH PRIVILEGES;