Best Practices for Default Transport Zones during VCF Deployment

Products

• VMware NSX

Issue/Introduction

During VMware Cloud Foundation (VCF) bring-up or Workload Domain deployment, the process may stall or fail validation if the NSX Overlay Transport Zone (TZ) is not marked as the "Default."

• The specific TZ (e.g., UUID aXXXXXXXXXXXXX exists but does not carry the
  "System Default" flag.
• Manual creation of the TZ was performed, but the is_default property was set to false.

Environment

VMware NSX

Cause

In NSX, the Default flag is a boolean attribute. When a Transport Zone is created manually via the NSX UI or API without explicitly enabling the "Set as Default" option, it defaults to false.


Why this matters: SDDC Manager automation workflows in VCF 9.0 expect a single designated "Default"
Overlay TZ to automate the creation of Segments and Tier-1 Gateways. If no TZ is marked as default, the automation cannot resolve which fabric to use for overlay traffic.

Resolution

1. The "SDDC First" Approach

The recommended best practice is to allow the VCF SDDC Manager to create the necessary NSX objects. This
ensures that names, UUIDs, and flags (including the Default flag) are set exactly as the orchestration engine
expects.

2. Manual Pre-configuration Checklist

If organizational policy requires manual TZ creation before the VCF team begins deployment, ensure the
following:

• Flagging: In NSX Manager, navigate to System > Fabric > Transport Zones. Edit the Overlay TZ and
  ensure "Set as Default" is checked.
• Single Default Rule: Verify that no other Overlay Transport Zone in the same NSX instance is marked
  as default. Only one Overlay and one VLAN TZ can hold this status.

Proactive Monitoring & Verification

API Verification Command

GET https://<nsx-manager-ip>/api/v1/transport-zones/<uuid>

# Look for the following in the JSON response: 
"is_default": true

Additional Information

Can this reoccur?
Yes. If the VCF team redeploys or adds a new NSX Manager instance and TZs are created manually without
setting the default flag, the deployment will slow down again at the validation phase.


Reference Technical Documentation
VMware Cloud Foundation 9.0 Documentation: Planning and Preparing for VCF Bring-up
NSX Administration Guide: Configuring Transport Zones and Profiles
VMware  Understanding NSX-T Transport Zones.
VCF Design Guide: Best Practices for Scalable Networking in Workload Domains.