A staple in OpenStack interview questions for experienced, be prepared to answer this one using your hands-on experience. A RabbitMQ broker is the logical grouping of many nodes where each node run the RabbitMQ application and share users, virtual hosts, queues, exchanges, bindings, and runtime parameters. A group of nodes is referred to as cluster. For seamless operation of RabbitMQ, all the data is replicated across all nodes within the OpenStack ansible for improved and high availability. The nodes interact with each other using domain names.   For creating a RabbitMQ cluster, there are two ways.  Manually using rabbitmqctl.  Specifying cluster nodes in a config, with rabbitmq-autocluster, or rabbitmq-clusterer plugins.