In a Multi-AZ (Availability Zone) setup for NetApp Cloud Volumes ONTAP in AWS, ensuring nondisruptive failover between nodes is critical for high availability. 'Floating IPs' are required for seamless failover between nodes in such a configuration.

Floating IPs allow the primary node to automatically transfer its IP address to the secondary node during a failover event, ensuring that clients can continue to access the service without needing to reconfigure anything. This mechanism enables clients to access the same IP regardless of which node in the cluster is actively serving requests, thus maintaining nondisruptive operations.

Elastic Network Interfaces (ENIs) facilitate networking in AWS but do not inherently handle IP floating between nodes for failover. Security groups and Intercluster UFs manage security and inter-node communication, respectively, but do not address the failover requirements. Floating IPs are explicitly designed to enable failover in high-availability cloud storage environments like NetApp Cloud Volumes ONTAP.

Thus, 'floating IPs' are the required network construct that allows for nondisruptive failover between nodes in a multi-AZ setup, ensuring continuous service availability even in the event of an outage in one availability zone.