Adding new APICs to broken cluster.

[summerSunshine]

I have a previously called ACI mini with one physical APIC and 2 vAPICs in L2 mode. We had to migrate from vMware and as a result, I have to add 2 newer physical APICs to the existing deployment.

Since the vAPICs are now gone and deleted from the cluster, I cannot perform a migration.

What is the best way to proceed?

Do I install the current software release, perform initial setup and then add the new APICs to the cluster?

[Daniel Slyk]

Hi,

I assume the first APIC in the cluster is a physical appliance?

Since the vAPICs have already been removed from the cluster, the only option is to bring the two new APICs to the same software version as the existing APIC, perform the initial setup, and have them join the current cluster. You are correct.

If you run into any issues during the process, feel free to share more details.

[Stefan Mihajlov]

@summerSunshine ensure new physical APICs match existing sw version exactly before running setup script with the original Fabric ID and parameters, one "ghost" vAPICs are decommissioned in GUI, u can register new node..

[mynetwork]

Hi @summerSunshine ,

The new APICs must run the exact same software version as the existing APIC
Node IDs must match the previously vacated vAPICs slots (typically nodes 2 and 3)

1. Match Software Version 
On your new physical APICs:
Install the exact same ACI version as the existing APIC

2. Clean / Fresh Setup on New APICs

On each new APIC:
Perform factory setup

Configure:
Fabric name (must match)
TEP pool (must match)
Infra VLAN (must match)
Discovery from Existing APIC

From the existing APIC GUI:
Go to:
Fabric → Inventory → Fabric Membership
You should see the new APICs as:
“Unregistered” / “Pending” nodes
Then:

Right-click → Register
Assign node IDs

4. Cluster Formation Happens Automatically
Once registered:
APICs will Download config, Sync database, Join cluster.

After both are added:
You regain 3-node cluster

Note: 👉 Install same version → perform initial setup → join existing fabric → register from current APIC