Tuning the Cluster Interconnect - Expert Oracle RAC Performance Diagnostics and Tuning - page 451

Figure 14-2. Assign network interfaces in Oracle 12c RAC

The number of HAIP addresses is decided by how many private network adapters are active when Oracle
clusterware gets started on the first node in the cluster. If there's only one active private network, Grid will create one;
if two, Grid will create two; and if more than two, Grid will create four HAIPs.

■ The number of haips won't change even if more private network adapters are activated later; a restart of
clusterware on all nodes is required for new adapters to become effective.

Note

Grid automatically selects link local addresses from reserved 169.254.*.* subnet for HAIP, and it will not
attempt to use any 169.254.*.* address if it's already in use for another purpose. With HAIP, by default, interconnect
traffic will be load balanced across all active interconnect interfaces, and corresponding HAIP addresses will be failed
over transparently to other adapters if one fails or becomes noncommunicative. 4
The database now records the private interconnect with the IP address 169.254.x.x .

4 Metalink Note # 1210883.1, 11gR2 Grid Infrastructure Redundant Interconnect, and ora.cluster_interconnect.haip .