Prior to Cisco APIC release 6.1(3), only clusters with physical APIC nodes supported standby APICs. Beginning with release 6.1(3), both physical and virtual APIC nodes support standby APICs. Standby APICs must be the same form factor (physical or virtual) as the active APICs in the cluster.

A minimum of three active APICs is required before adding a standby APIC.

The standby APIC must be running the same firmware version as the cluster when it joins during initial setup.

After all active APICs are upgraded during a software upgrade process, the standby APICs are upgraded automatically.

During initial setup, IDs are assigned to standby APICs. If a standby APIC is promoted to active status, it adopts the ID of the APIC it replaces.

Administrative login is not enabled on standby APICs. To troubleshoot a standby APIC, log in using SSH as the `rescue-user`.

During a switchover, the replaced active APIC must be powered down to prevent connectivity issues.

Switchover may fail in these cases.

• There is no connectivity to the standby APIC.

• The standby APIC firmware version does not match the active cluster.

After switching over a standby APIC to active, you can set up another standby APIC if necessary.

If you check the option 'Retain OOB IP address for Standby (new active),' the standby APIC promoted to active retains its original out-of-band (OOB) management IP address.

• If only one active APIC is down, the standby (new active) APIC uses the old active APIC's OOB management IP address.

• If more than one active APIC is down, the standby (new active) APIC attempts to use the old active APIC’s OOB management IP address. However, this may fail if the IP configuration data is in the minority state.

For Cisco ACI Multi-Pod deployments, if the old active and standby APICs use different OOB management IP subnets, be sure to check the option to retain the original standby OOB management IP. Otherwise, OOB connectivity may be lost. If connectivity is lost due to this or if multiple active APICs are down, create a new static node management OOB IP and make sure your cluster is not in the minority state.

The standby APIC does not participate in policy configuration or management.

The system does not replicate any information, including administrator credentials, to standby APICs.

A standby APIC does not retain its in-band management IP address when promoted to active. You must manually reconfigure the in-band management IP address on the newly active APIC.