Readable Secondary AG databases internally use snapshot isolation under the covers. This will enable read-only workload to run against secondary databases.
Total : 6 – 7
1 for WSFC cluster network name
1 for SQL Server instance network name
2 (1 on each node) for private/internal/heartbeat network among cluster nodes
2 (1 on each node) for public network access
1 for MSDTC (if MSDTC is configured as clustered service)
2 (1 for each node) for iSCSI HBA/network adapter for communication to SAN (if iSCSI SAN is used).
HBA is used for offloading iSCSI TCP/IP traffic processing from CPU