Primary Host Attach Port This is the WWPN that communicates with hosts. It is a target port  only, and this is the primary port, so it represents this local node’s  WWNN. Failover Host Attach Port This is a standby WWPN that communicates with hosts and is only  brought online on this node if the partner node in this I/O Group goes  offline. This is the same as the Primary Host Attach WWPN on the  partner node. NPIV port Description Figure 5-36 shows the three WWPNs that are associated with a SAN Volume Controller port  when NPIV is enabled. The failover host attach port (shown in pink in Figure 5-36) is not active at this time.  Figure 5-37 on page 248 shows what occurs when the second node fails. Subsequent to the  node failure, the failover host attach ports on the remaining node are active and take on the  WWPN of the failed node’s primary host attach port. Note:  Figure 5-37 on page 248 shows only two ports per node in detail, but the same  applies for all physical ports. Figure 5-36 Allocation of NPIV virtual WWPN ports per physical port Chapter 5. Host configuration  247