change master 'master1' to 
master_port=MYPORT_1, 
master_host='127.0.0.1', 
master_user='root';
start slave 'master1';
set default_master_connection = 'master1';
include/wait_for_slave_to_start.inc
drop table if exists t1;
create table t1 (i int) engine=MyISAM;
mysqld-relay-bin-master1.000001
mysqld-relay-bin-master1.000002
mysqld-relay-bin-master1.index
show relaylog events in 'mysqld-relay-bin-master1.000002';
Log_name	Pos	Event_type	Server_id	End_log_pos	Info
mysqld-relay-bin-master1.000002	4	Format_desc	3	246	Server version
mysqld-relay-bin-master1.000002	246	Rotate	1	0	master-bin.000001;pos=4
mysqld-relay-bin-master1.000002	290	Format_desc	1	246	Server version
mysqld-relay-bin-master1.000002	532	Binlog_checkpoint	1	286	master-bin.000001
mysqld-relay-bin-master1.000002	572	Query	1	400	use `test`; DROP TABLE IF EXISTS `t1` /* generated by server */
mysqld-relay-bin-master1.000002	686	Query	1	500	use `test`; create table t1 (i int) engine=MyISAM
show relaylog events;
Log_name	Pos	Event_type	Server_id	End_log_pos	Info
mysqld-relay-bin-master1.000001	4	Format_desc	3	246	Server version
mysqld-relay-bin-master1.000001	246	Rotate	3	304	mysqld-relay-bin-master1.000002;pos=4
drop table t1;
include/reset_master_slave.inc
include/reset_master_slave.inc