Netterene

ACI Leaf Switch Replacement

 To replace a Cisco ACI
leaf switch, follow these step-by-step instructions to ensure
a smooth transition without disrupting your fabric:

🛠️ Preparation

  1. Document the existing switch details:
    • POD ID
    • Node ID
    • Node Name
    • Serial Number 
  1. Ensure the replacement switch is in ACI
    mode    :
    • Connect via console and run show
      version.
    • If in NX-OS mode, convert to ACI mode
      using Cisco’s documented procedure 
    • Before adding the new leaf switch to the
      fabric, ensure it’s manually upgraded to the target image or one with a
      direct upgrade path. Avoid using intermediate images that require
      multiple upgrade steps, as they can trigger issues and impact your
      production environment. A final upgrade via policy helps ensure BIOS
      and FPGA components are properly updated.
  1. Clean up the replacement switch:
    • Run setup-clean-config.sh and
      then reload to remove any existing configuration 

🔄 Decommission the Faulty Leaf Switch

  1. Go to APIC GUI:
    Fabric > Inventory > Fabric Membership
  2. Right-click the faulty switch → Select Decommission.
  3. Once decommissioned, Remove from
    Controller     and confirm the action 
  4. Physically disconnect and unmount the old switch.

🔌 Install and Connect the New Leaf Switch

  1. Mount the new switch and connect uplinks to spine switches. DONOT CONNECT DOWNLINK AT THIS STAGE
  2. Power on the switch.
  3. In APIC GUI, go to:
    Fabric > Inventory > Fabric Membership > Nodes Pending
    Registration
  4. Verify serial number, then Register the
    switch:
    • Use the same POD ID, Node ID, and
      Node Name       as the old switch 
  1. Once registered, go to:
    Fabric > Inventory > Fabric Membership > Registered Nodes
    → Right-click → Select Commission.
  2. Wait for the switch to reach Active state.

🔍 Post-Replacement Validation

  1. Connect downlink cables (after
    switch is active).
  2. Go to:
    Fabric > Inventory > Topology
    → Verify the switch is visible and operational.
  3. SSH into APIC and run:

→ Confirm switch
status is active 

  1. If you get SSH warnings (e.g., DNS
    spoofing), update the known_hosts file:

🧩 Troubleshooting Tips

  • Switch not discovered: Check LLDP neighbors and cable
    connections.
  • Switch shows “Not Supported”: Upgrade APIC firmware to match switch
    model.
  • No TEP IP assigned: May be a DHCP issue—contact Cisco TAC.
  • SSL issues: Check for established sessions on port
    12215