An active/active clustering provides high availability and load balancing when deployed with an external load balancer. An active/active cluster deployment requires an external device to distribute the load among the members because the cluster does not have a VIP address. The load balancing devices are equipped with algorithms that balance the load, as well as detect whether a device is down.Active/active configuration allows increased aggregate system throughput as well as seamless fail-over, which is achieved by state synchronization between the two devices for all the configurations so that the devices are virtually identical.
NOTE: This feature provides increased throughput and performance for peak load characteristics by sharing load; however, it does not provide increased scalability beyond the maximum license Limits
For more information, refer 9.1R4 Admin guide section Deploying an Active/Active Cluster
Node specific VPN IP pool :
We can configure Node specific IP pools as below :