Expanding the Cisco Fabric Controller clusters is an administrative operation that

• increases the cluster size from N to N+1 within approved limits,

• requires the operator to set the desired administrative cluster size and connect controllers with the correct cluster IDs, and

• enables the cluster to automatically perform the expansion.

Expanding clusters accommodates network growth and helps maintain redundancy and performance by including additional controllers as the needs of the organization change.

Expanding the Cisco APIC cluster is the operation to increase any size mismatches, from a cluster size of N to size N+1, within the boundaries. The operator sets the administrative cluster size and connects the APICs with the appropriate cluster IDs, and the cluster performs the expansion.

During cluster expansion, regardless of in which order you physically connect the APIC controllers, the discovery and expansion takes place sequentially based on the APIC ID numbers. For example, APIC 2 is discovered after APIC 1, and APIC 3 is discovered after APIC 2 and so on until you add all the desired APICs to the cluster. As each sequential APIC is discovered, a single data path or multiple data paths are established, and all the switches along the path join the fabric. The expansion process continues until the operational cluster size reaches the equivalent of the administrative cluster size.