The following block of the configuration can be used to distribute requests between the RabbitMQ servers:

listen rabbitmq-webapi *:15672
 mode tcp
 balance roundrobin
 option tcplog
 server server-01 server-01:15672 check port 15672
 server server-02 server-02:15672 check port 15672
 server server-03 server-03:15672 check port 15672

listen rabbitmq-backend *:5672
 mode tcp
 balance roundrobin
 option tcplog
 server server-01 server-01:5672 check port 5672
 server server-02 server-02:5672 check port 5672
 server server-03 server-03:5672 check port 5672