Explanation
https://portal.nutanix.com/page/documents/details/?targetId=Web_Console_Guide-Prism_v4_7:lic_licensing_ma Reclaiming Licenses (Including License Renewal)You can reclaim and optionally re-apply licenses for nodes in your clusters:
* You must reclaim licenses when you plan to destroy a cluster. First reclaim the licenses, then destroy the cluster. You do not need to reclaim Starter licenses. These licenses are automatically applied whenever you create a cluster, including after you have destroyed a cluster.
* Return licenses to your inventory when you remove one or more nodes from a cluster. Also, if you move nodes from one cluster to another, first reclaim the licenses, move the nodes, then re-apply the licenses.
* You can reclaim licenses for nodes in your clusters in cases where you want to make modifications or downgrade licenses. For example, applying an Ultimate license to all nodes in a cluster where some nodes are currently licensed as Pro and some nodes are licensed as Ultimate. You might also want to transition nodes from Ultimate to Pro licensing.
* You must reclaim licenses when you renew licenses. First reclaim the expired licenses, then apply new licenses.

An IP address is assigned from the pool of addresses when a managed VM NIC is created; the address is released back to the pool when the VM NIC or VM is deleted. Be sure to work with your network team to reserve a range of addresses for VMs before enabling the IPAM feature to avoid address overlap.
Reference: https://next.nutanix.com/blog-40/virtual-networks-for-virtual-machines-in-acropolis-hypervisor-6640