The standard documentation and tutorials on MMM for MySQL, for master-master replication setup, suggest one Virtual IP for the writer role, and two Virtual IPs for the reader role. It can be desired to only have a single virtual IP for the reader role, as explained below.
The two IPs for the reader role
A simplified excerpt from the mmm_common.conf sample configuration file, as can be found on the project’s site and which is most quoted:
[Read more...]... <host db1> ip 192.168.0.11 mode master peer db2 </host> <host db2> ip 192.168.0.12 mode master