Flow control configuration is an important validation step in ONTAP SAN and NAS environments, especially in switchless cluster designs. NetApp documentation clearly differentiates flow control requirements between data networks and cluster networks.

For data network ports, full flow control must be enabled when hosts are configured with full flow control. This ensures proper congestion management and prevents packet loss during high-throughput NAS operations such as NFSv4.1 and SMB traffic. Matching flow control settings between hosts and storage data ports is a best practice explicitly stated in NetApp installation guidance.

In contrast, cluster network ports must have flow control disabled. The cluster network is highly sensitive to latency and congestion, and enabling flow control on cluster interconnect ports can introduce delays that negatively affect cluster quorum, node communication, and overall stability. NetApp explicitly requires flow control to be disabled on cluster network interfaces.

Enabling flow control on cluster ports or disabling it on data ports would violate NetApp-supported configurations and can lead to performance degradation or cluster communication issues.

Therefore, the two correct settings to verify are:

Data network ports have full flow control enabled

Cluster network ports have full flow control disabled

This makes C and D the correct answers.