mmm_common.conf with 3 masters

active_master_role                      writer

<host default>
        cluster_interface               bond0
        pid_path                        /var/run/mysql-mmm/mmm_agentd.pid
        bin_path                        /usr/libexec/mysql-mmm/

        replication_user                replication
        replication_password            replicationpassword

        agent_user                      mmm_agent
        agent_password                  agentpassword
</host>

<host db1>
        ip                              10.0.0.1
        mode                            master
        peer                            db2
</host>

<host db2>
        ip                              10.0.0.2
        mode                            master
        peer                            db1
</host>

<host db3>
        ip                              10.0.0.3
        mode                            master
        peer                            db1
</host>

<role writer>
        hosts                           db1, db2, db3
        ips                             10.0.0.4
        mode                            exclusive
</role>

<role reader>
        hosts                           db1, db2, db3
        ips                             10.0.0.5, 10.0.0.6, 10.0.0.7
        mode                            balanced
</role>