There two type of connections that they needed. (Control connection and data connection)
If the backup application supports Cluster Aware Backup (CAB), you can configure NDMP as SVM-scoped at the cluster (admin SVM) level, which enables you to back up all volumes hosted across different nodes of the cluster. Otherwise, you can configure node-scoped NDMP, which enables you to back up all the volumes hosted on that node.
Configuring LIFs
You must identify the LIFs that will be used for establishing a data connection between the data and tape resources, and for a control connection between the admin SVM and the backup application. After identifying the LIFs, you must verify that firewall and failover policies are set for the LIFs, and specify the preferred interface role.
https://library.netapp.com/ecm/ecm_download_file/ECMLP2496247
Does it make sense to you now?