Expanding a cluster across multiple racks in VMware Cloud Foundation (VCF) enhances both capacity and resilience for workloads. Traditionally, extending Layer 2 (L2) networks across racks has been complex and often discouraged due to potential issues with broadcast domains and network stability. However, VCF introduces a streamlined approach to achieve this expansion without the need for L2 extension, leveraging its robust API capabilities.

Understanding VCF Network Types and Clusters

In a VCF environment, ESXi hosts connect to various networks, categorized into:

• VM Networks: These networks connect virtual machines (VMs) essential to the VCF infrastructure, such as SDDC Manager, vCenter servers, and NSX managers.
  • VM Management Network: Provides management connectivity for infrastructure VMs.
  • Edge TEP Network: NSX Edge VMs are used to connect to NSX segments.
  • Edge Uplink Networks: Provide VLANs for connecting the Tier-0 gateway to physical routers.
• ESXi Host Infrastructure Networks: These networks connect the vmkernel interfaces of ESXi hosts.
  • Management Network: Used to manage the ESXi host.
  • vMotion and vSAN Networks: Defined collectively within a network pool in VCF, used by vMotion and vSAN features.
  • Host TEP Network: Used by ESXi hosts for implementing NSX segments.

While VM networks require L2 extension across racks to support VM mobility and high availability, ESXi host infrastructure networks typically do not, as ESXi hosts are physical devices with fixed IP addresses linked to their rack locations. However, VCF configuration may require spanning these networks across racks if the cluster is being expanded.

Expanding a Cluster Without L2 Extension

VCF enables cluster expansion across racks without the need for L2 extension by utilizing its API. This approach simplifies the process and reduces reliance on complex physical network configurations.

Steps to Expand a Cluster Across Racks:

• Prepare the New Rack:
  • Ensure the new rack meets the hardware and network requirements specified by VCF.
  • Verify that the ESXi hosts in the new rack are compatible with the existing cluster
•  Configure Network Settings:
  • Set up the necessary VM networks in the new rack, ensuring they align with the existing network configurations.
  • Configure ESXi host infrastructure networks as required, considering the need for potential L2 extension based on the cluster’s configuration.

• Use VCF API for Cluster Expansion:
  • Utilize the VCF API to add the new ESXi hosts to the existing cluster.
  • The API facilitates the expansion process without the need for manual L2 network adjustments.
• Validate the Expansion:
  • After the expansion, perform thorough testing to ensure that workloads are distributed correctly and that the cluster operates as expected.
  • Monitor the performance and stability of the expanded cluster to identify and address any issues promptly.

Benefits of This Approach:

• Simplified Network Configuration: By eliminating the need for L2 extension, the complexity of network setup is reduced, leading to a more straightforward deployment process.
• Enhanced Automation: Leveraging the VCF API streamlines the expansion process, allowing for automated and consistent cluster growth.
• Improved Resiliency: Expanding clusters across racks enhances workload resiliency by distributing resources across different physical locations, reducing the risk of simultaneous failures.

For a detailed guide on expanding a cluster across racks in VMware Cloud Foundation,

refer to the original article: Expand a cluster across racks in VMware Cloud Foundation.

By adopting this approach, organizations can achieve a more flexible and resilient infrastructure,

aligning with modern data center designs that prioritize scalability and high availability.