How to Add Additional VLANs to a Cisco HyperFlex Cluster

 In environments running Cisco HyperFlex, it's often necessary to add new VM-Network VLANs as applications scale or new services are introduced. While UCS Manager and vCenter provide some control over networking, the correct and supported way to add new VM-Network VLANs to an existing HyperFlex cluster is through the HyperFlex Installer.

This guide walks through the precise steps required, ensuring your VLANs are properly integrated into the cluster configuration through HyperFlex Installer.

Prerequisites

Before proceeding, ensure the following:

1. You have SSH access to the HyperFlex Installer VM.
2. You know the HyperFlex Cluster IP or FQDN.
3. You have administrative credentials for:
   
   • HyperFlex CVM
   • vCenter
   • ESXi hosts (root password)
4. The new VLAN IDs are known and trunked upstream to the Fabric Interconnects.

Note: If the HyperFlex Installer VM is missing or was previously removed, you can download the official HyperFlex Installer OVA from Cisco’s Software Download portal and deploy it on your vCenter. Ensure you download the version that matches your HyperFlex cluster.{alertInfo}

Step-by-Step: Adding VLANs via HyperFlex Installer

Step 1: Access the Installer VM

1. SSH into the HyperFlex Installer VM:
   

   ssh root@<installer-vm-ip>{codeBox}

2. Once logged in, run:
   

   hx_post_install{codeBox}

Step 2: Select the Workflow

You'll be prompted to select a workflow:

1. New/Existing Cluster
2. Expanded Cluster
3. Generate Certificate{codeBox}

Choose:

1. New/Existing Cluster

Step 3: Provide Cluster and vCenter Info

You will be asked to provide:

• HyperFlex Cluster IP or FQDN
• CVM admin password
• vCenter FQDN or IP
• vCenter admin username and password

If DNS is not working, ensure /etc/resolv.conf is correctly configured in the installer VM and that hostnames resolve with nslookup or getent hosts.{alertInfo}

Step 4: Validate ESXi and vCenter Details

The installer will pull details about:

• Datacenter name
• Cluster name
• List of ESXi hosts

This step ensures the installer can connect and update configurations.

Step 5: Enter ESXi Root Password and Choose Option

Next, you'll be asked for the ESXi root password for all hosts. After authentication, you’ll be presented with a series of optional configuration prompts:

Enter vSphere license key? (y/n)         → Type n and press Enter.

Enable HA/DRS on cluster? (y/n)          → Type n and press Enter.

Disable SSH warning? (y/n)               → Type n and press Enter.

Add vmotion interface? (y/n)             → Type n and press Enter.

Add VM network VLANs? (y/n)              → Type y and press Enter.{codeBox}

Important: Only the last option is relevant to our goal. The others should be skipped unless you're also updating HA/DRS or licenses.{alertSuccess}

Step 6: Provide UCSM IP Address and Credential

You'll be prompted to enter UCSM IP Address, username, and password.

Step 7: Add Your New VLANs

Now you can add your desired VLANs:

• Input HX Sub Organization.
• Input Port Group name.
• Input the VLAN ID (e.g., 822).
• Add VLAN to VLAN Group (optional).

Repeat this for all additional VLANs you want to create.

Step 8: Commit and Reconfigure

Once VLANs are added:

• The installer will reapply configuration to ESXi hosts.
• VLANs will be registered with vCenter and UCS.
• No service interruption occurs if changes are within scope (i.e., adding networks, not changing boot or storage VLANs).

Validation

After the process:

1. Log into vCenter and verify new port groups were created under the distributed switch.
2. Confirm on UCS Manager that new VLANs appear under LAN > VLANs.
3. Deploy a test VM to each new network and confirm connectivity.

Conclusion

Using the HyperFlex Installer and hx_post_install is the correct and Cisco-supported method to add VM-Network VLANs in a HyperFlex environment. This ensures consistency across UCS, vCenter, and HyperFlex software-defined infrastructure.

Avoid making changes directly via UCSM or vCenter, as it may lead to configuration drift or unsupported states.{alertWarning}