Heartbeat packets that are sent over the cluster interconnect are not IP based. As a result, these packets cannot be routed. If you install a router between two cluster nodes that are connected through cluster interconnects, heartbeat packets cannot find their destination. Your cluster consequently fails to work correctly.
To ensure that your cluster works correctly, you must set up the cluster interconnect in the same layer 2 (data link) network and in the same broadcast domain. The cluster interconnect must be located in the same layer 2 network and broadcast domain even if the cluster nodes are located in different, remote data centers. Cluster nodes that are arranged remotely are described in more detail in Chapter 7, Campus Clustering With Oracle Solaris Cluster Software.